Sounds good! Good luck with the new playthrough too!
Actually, since you've played mage before, maybe several times, when do you typically start to specialise in a class, or rather, use the intended class' weapon? Not until Hardmode, or do you go with whatever magic weapon you can find or craft pretty much right away?
I'm not very strict about things like "only mage weapons", because then it could turn very tough, looking for a
wand of sparkling. You might find one early, but sometimes you just don't find any...
But then again, I like to use melee weapons too, so, I usually go like.
Start. Craft a wooden sword. (wooden armor is irrelevant. maybe craft a bow too for early game.) build up, a house with like 2 rooms for the start, then add more rooms, and more houses later. Then, just generally scout the area. If you're lucky enough to have a cave nearby, it can be great. If not, then just start to mine downwards somewhere XD You can try to look for treasures, basically any gold chests can be a good find, though some items aren't very useful, but, things like cloud in a bottle or magic mirror can be a huge help - but you already know that anyway.
For mage, I think, the top priority to look for are
gemstones. As well as
cobweb. Try to gather all cobwebs you find, and make
silk, and once you have enough for a robe, craft one. the basic silk robe is just vanity, but it can be crafted into
gem robes, that give you lots of mana. even the lowest tier (amethyst) is great, so, whichever gemstone you find enough of to craft into the robe, craft it. You can replace it with a higher tier later, but for start, any can be good. That most likely means amethyst or topaze, as they're the most common at the higher depths (so, closer to the surface).
You can try to make amerthyst/topaze rod, but they're really garbage sadly. emerald and sapphire are only a bit better, but still not really good. So, the
top priority of gems are rubies and diamonds - both which are pretty rare... additionally, it somewhat depends on what ores your world has. the ruby staff needs gold bars, and the diamond staff needs platinum bars in addition to the gemstones, so, if your world has gold, look for rubies, and if your would has platinum, look for diamonds.
Of course, bars can be aquired from crates too, but still.
You can have a bit better luck in other biomes. The ice caverns tend to have more gems, so if you're looking for them, you might find some there, but a
desert expedition might pays off more nicely.
Although the underground desert is a dangerous place, but if you can survive there, it's a great place to quickly gather some very good starter gear for a mage.
While it's not rich in most gemstones, its "native" gemstone,
amber can be found there in great quantities. There's also fossil in huge veins, you can mine, and extractinate if you got an extractinator - it can be found in the desert often too, though you're not always lucky enough that there's one nearby... But even if you have no luck finding an extractinator, the desert worms may drop 1~2
sturdy fossils. you can get them from extractinating fossil too, but, so, if you have no luck with an extractinator, you might get just enough fossils from the worms while looking for other treasures there.
The
amber staff has similar stats to the ruby staff. So, theoretically, diamond is a tiny bit stronger, but amber should be powerful enough if you can't get diamonds. All 3 (ruby, amber, diamond) has autoswing, and pierces up to 2 enemies (well, like, goes through one, and disappears upon hitting the 2nd)
They all have very low mana cost to use, so they're really ideal for early-game mages. They're strong, and the autoswing makes them very convinient to use. With a good modifier, they can easily carry you up to Skeletron!
They also sync well with gem robes, because gem robes give you tons of mana, so you can keep using the staves for very long before you run out of mana.
If you decide on an early-game desert exploration, you can get both the
amber robe and the amber staff quite early, and they should do for pre-bosses, basically. you need good mobility and lots of HP and stuff against EoC, but the amber staff should work well there. - and you might find
another interesting mage weapon in a desert chest too.
Since you're in a crimson world, there's no vilethorn, but you might get a
crimson staff, which can give a little bit of additional fire - or water XD - power. Though, the main thing to look for from crimson hearts is the
panic necklace, to craft a band of starpower from.
For later pre-hardmode progression, there are basically 2 mage armors for pre-hardmode, besides the gem robes -
jungle armor, which you can make pre-bosses, if you can get the materials. It's dangerous, but doable. It's an armor more focused on giving lots of additional mana.
The other main option is
meteor armor, from meteor bars, which you can aquire after BoC there. Meteor doesn't gives you as much additional mana, but I think boost your attack a bit more than jungle armor. Additionally, meteor armor works well with the
space gun, a magic gun, because it has no mana cost to use, while wering that armor.
Both are pretty good, and should work fine until early hardmode, where early-harmode tier metals become available (forbidden armor might be an interesting possibility too, at that point, besides the normal early-hardmode ore armors)
The gem staves and a few other weapons can carry you until skeletron, though expert skeletron is very very tough at first - the
bee gun might coes hand there - but
the dungeon offers a few nice late pre-hardmode mage weapons, and there are some in shadow chests too (or obsidian lock-boxes)
Ah, and, if you don't do pure mage, and wanna carry around other weapons too, when it comes to melee, you might want something that naturally has autoswing.
mandible blade for example is pretty decent - and you might get one from a desert exploration anyway. it's a rather small sword, but it has autoswing and relatively fast too, so it's quite handy for early game, for a battle mage. A warrior might looks for bigger swords, but if you have no feral claws, most early game swords has no aotoswing. You can equip a feral claws too though, but you might wanna use that slot for something else. Naturally, stuff like katana works great too, if you're lucky enough to have the traveling merchant have one for sale.
Ah, but for very early game, a
sickle does just as well. You can buy it from the merchant, it's not even expensive, and while it might be considered a tool to gather hay, it has autoswing, making it a very useful "sword" for the start of the game. Additionally you gather a bunch of hay, which can be useful for buildings, for example if you like hay roofs XD I know I love using it for roofs.
If the desert is indeed the first target to travel to, setting up a desert town and a forest town and aquiring their respective
pylons can make traveling back-and-forth a lot quicker and convinient. A jungle town could come in very handy too (you also wanna get stuff like lots of moonglows relatively early, not to mention the stuff for the jungle armor), but in general, having several towns, like cavern, etc. can just help a lot with traveling.
Also, you would expect that mages are glass-cannons, but they aren't. well, in expert, defense matters much less, and they're certainly much less tanky than warriors, but they have decent defense too, once having jungle/meteor armor. You might wanna keep your gem robes too tough, if you like them as vanity or something. They can look awesome dyed too. Lately I realised how fascinating amber robe looks like, dyed with black-and-white dye. It looks like a frilly gothloli robe, might gives a good looks for a mage or something, maybe with a mage hat, or some pretty hair adornments.
But you can go for armors too, or anything. Vanity can make the character look more unique and helps giving them a "character", or how to say. You usually just wear whatever you find on first playthrough, but later, you might wanna go for more specific looks, something stylish related to the class, or whatever other things related to the character - like a Gi for a "ninja", or metal armor for a "knight", or whatever - or even just something entirelly different. Because, I think, it kind of works like, the first playthrough is kind of "your" adventure, and the character's looks usually isn't high priority. You might wanna aim for them to look cool, but you usually just pick up whatever you find. but from the 2nd playthrough onwards, it works a bit like "I created this character. I named him X. this is the story of X." and so, said "X" needs (well, a name too, of course XD lol, but, also, a sort of looks too, right? a garment, a hairstyle, whatever stuff, to look like that main character you want for their story. It's not a must, but I think you can connect a lot more with the characters that way. And its fun if they have their own, unique looks. IMO.
Edit: nearly forgot.
If you plan an early desert expedition, stock up on
granades! They're not magic weapons of course, but they're very powerful and extremely useful there. So, get the demolitionists as soon as possible, and buy at least one stack of granades. be careful using them, but when it comes to the underground desert, it often happens your path is blocked by a horde of antlions below. taking them out without any long-range weapons is very tough if you have no, or just minimal defense, but as long as you're in safety, you can dispatch them with a few hand granades quickly.
Granades also works wonderful against the goblin army, since area dmg. offers awesome crowd-control.
And they can be crafted into variants such as sticky granade, which sticks to the surface of where you threw it, and and does area dmg. (but doesn't destroys blocks like bombs) - you can use them for example to clear out the combies knocking on your door. as long as they can't come inside (if there's a firniture right next to the door on the inside, zombies or such won't be able to open it even at blood moons. but so, they can't come in, but you can't get out either when there are 23 zombies at your door, but like 3 sticky granades right on the door, and you don't need to worry about those zombies anymore. the area dmg gets them on the other side of the door.