Looking around for some weapon and armor diagram tips. I know of a few you can get pretty early on (because I just sort of stumbled across them lol) But I'd like to hunt for the others.

So let me know what diagrams you've found, or link me to any references you've used :D

looking for witcher gear can be quite annoying, you most likely will end up using a guide to find the quests. i read the quest guides and made a note next to my witcher backup after some testing. the locations are:-

oxenfurt harbour - velen - armourer (oxenfurt top half)
kaer trolde - skellig - armourer (main skellig port)
blackbough - velen - merchant (closest to marker) & Blacksmith (west of crow's perch)
crows perch - velen - merchant (near quest armourer)
lindenvale - velen - blacksmith (east of crow's perch)
midcopse - velen - armourer (southwest of crow's perch)
hierarch square - novigrad - armourer (centre)
hattori

You should probably know that Witcher gear is level based, so you need to search for them when you are at an appropriate level. Numbers are for basic, enhanced, superior and mastercrafted.

Griffin School armour - level 8, 15, 22, 31
Feline School armour - level 14, 20, 26, 31
Wolf school armour - level 14, 20, 26, 31 <---- (you can't start to use this until you have access to Kaer Morhen)
Ursine School Armor - level 17, 22, 27, 31

Griffin School sword - level 7, 14, 21, 30
Feline School sword - level 14, 19, 25, 30
Wolf school sword - level 14, 19, 25, 30 <---- (you can't start to use this until you have access to Kaer Morhen)
Ursine School sword - level 15, 21, 26, 30

that reminds me. you also get manticore and grandmaster level gear but they're independant from the others (as in you don't upgrade from the previous edition of the armour and sword if i recall correctly) those are quest based items in blood and wine expansion and don't require you to go hunting outside the quest unlike the ones previously mentioned so you should be ok for these.

you get viper gear from hearts of stone expansion when you go to the auction house. without trying to spoil the quest for you, you will find that you can do several optional things while at the auction house. speaking to a particular someone will give you access to some viper content. i can't remember if it is swords and armour or just one of them. you have to pick up the venomous viper sword when in the vault by looting the right thing. so that's 2 things you need to do while at the auction house

lastly you'll meet a witcher who is not known to geralt as part of a quest. your choices will either get you another unique piece of a witcher sword or not.