Well, as someone who's done about three regular summoner playthroughs, a summoner whips only, and a summoner summons only playthough, and an avid summoner main. Im gonna tell you to go for it. whips add a large ammount of damage and range to your arsenal, even more so with whip stacking. (hitting with one whip, and switching back to your more powerful whip. most commonly used for damage buffs to your minions and for a variety of effects you gain on hit with the whip). But, mastermode can be quite the challenge and leaving you feeling frustrated, so heres some tips. :
If you find yourself having trouble with a boss, take a break. be it playing on a different world with a class you perfer more, or just laying in bed. usually when i do this it leaves me feeling refreshed and ready to take on the challenge, and i win.
Be prepared for ALOT of fishing. if your going with a linear guide, then your gonna need to do alot of fishing, for summoner potions, buffs, and items you can obtain by killing a fished up enemy like the vampire frog staff, or sanguine staff.
If you find yourself having trouble with stacking alot of whips, then minimize it to just two or dont even whip stack if you dont feel good enough. My favorite whips to stack are the kolaidescope (main damage), durendal (whip speed), and the frozen whip(?) (the icecicle deals alot of damage to bosses such as plantera with her minions, and its good till cultist, at that point you probably just want to use the dark harvest and kolaidescope.)
You do not have to defeat daytime empress. The stardust dragon and spooky armor with the kolaidescope is PLENTY enough to defeat the moonlord, if you please then you can, but i wouldnt reccomend it, ive only managed to do it once. However, if you do manage to kill daytime empress, then use all your summon slots kolaidescope, and then summon the dragon three times, this maximizes your dps.
Final tip, be prepared to fight bosses alot. most of the time you wont get exactly what you want or whats best for the summoner class, i have to beat the wall of flesh on average about five times for the firecracker. And also, NEVER USE THE OFFICIAL WIKI! the guides arent good, they just tell you what kind of works and expect you to beat the game like that, its best to follow a guide on youtube or such.
now, heres my tips for progression just for you to get an idea of how summoner works.
Pre boss - Flinx fur coat, Gold / Platinum helmet and greaves, Snapthorn, Flinx staff.
Post evil boss - Obsidian armor (if you perfer using whips over summons) / Bee armor (if you perfer your summons do the damage instead of whips), Snapthorn. Hornet staff / Imp staff, Pygmy necklace
Pre wall - Spinal tap, obsidian / bee armor, spinal tap, hornet / imp staff, Pygmy necklace
Pre mech - Spider armor, Frozen whip, Spider staff / Sanguine staff / Blade staff (spider staff is mostly good for the destroyer if one spider latches onto a different segment, due to the twins and skeletron's flight, the spiders cannot latch onto them) Summoner emblem, pygmy necklace.
Pre plantera - Hallowed armor, Durendal / Frozen whip (if you stack them, it shreds plantera no problem.) pygmy necklace, avenger emblem, summoner emblem, Blade staff.
Pre golem - Spooky armor, Kolaidescope / Durendal / Frozen whip (stacking all three of these will have you set for the rest of the game), Pygmy necklace, herculese beetle, papyrus scarab, necromantic scroll, blade staff / terraprisma (if you feel confident enough to get it)
(Just use your golem setup for cultist, it actually works really well)
Moonlord - Stardust dragon staff / Terraprisma. Durendal, / kolaidescope / Dark harvest. Pygmy necklace, herculese beetle, papyrus scarab, necromatic scroll.
Hope this helped! (all this work spent on a dead post... atleast i helped you...? ill just copy and paste it and use it for other aspiring summoners LOL!)