Crafting is mandatory imo, unless you're in a guild with people who will give you stuff. Sure, you can find decent-ish gear, and some quests and dungeons will reward you with a nice blue+ piece now and again, but you can craft stuff with excellent set bonuses, and make sure you have decent armour in every slot, and it costs you nothing but the time to gather materials, research traits, and craft it.
To be any good at crafting, you'll need to invest skill points in the passives related to the craft you want to level. With that in mind, it can be difficult to level all crafts on a character you actually want to play the game with, since there are a finite number of skill points available. Epona's good advice was to have all the armour/weapon crafts on one character (clothier, blacksmithing, woodworking) and everything else on another (provisioning, alchemy, enchanting). That's what I'm doing, although it's very easy to level up provisioning without investing many points so I reckon you should just do that on all your characters anyway.