Gearing up in this game...

[Celerity]

I am a spider, and I don't think I'd put gems or paintings in the "easy" category, as they require several other tradeskills to obtain..

Beast forms are harder to do than the traditional humanoid skills and you seem to have pulled the short straw since spider is definitely the hardest skill trainer to favour in the entire game.

I consider gems easy since they give ~20 favour each and can be bought in player vendors for even as cheap as 160 each, so for friends you need 300/20 = 15 gems which is a cost of 15 * 160 = 2.4k. This is a rough calculation of course because it differs for each individual npc and depends on your bonuses from civic pride and notoriety. Gems would be difficult if you tried to survey them all yourself, since you don't get many of any one specific gem easily but since you can just buy them so cheaply off player vendors I don't think it's an issue.

I also consider paintings easy since you can farm high value paintings from the red wing of the goblin dungeon annex and normally coming back with a full inventory is enough to favour an npc to close/best friends and then doing a second run and maybe a third gives you enough to get like family, which is the highest favour you'll basically ever need from any of the skill unlock trainers. Now of course you'll have to put some effort into learning and training art history but the very act of training the skill gives you the paintings you need for favour.