I’m no expert by any means, but I’ve had these same questions over the time I’ve played the game.
Bigger flasks seem to nearly always be better, all other things (magical properties) being equal. At the high end it seems there is some trade off between amount restored and rapidity of restoration, but I’m not 100% sure about that. In general, at the levels I’ve been playing at (to the mid 40s) bigger is better.
Wisdom scrolls accumulate over time, especially after you stop having to ID everything to see if it’s an upgrade. My stash is chock full of them. Since I started using a loot filter, too, it makes it quite a bit easier to just gather what I need rather than everything; I don’t ID a lot of crap that falls because I don’t even pick it up. Some might say ID all the blues, but I think that applies if you’re looking for something specific; if you’re a wand user, there’s little need to ID a one-socket blue two-handed sword (or even pick it up in the first place).
I’ve kept using rares or uniques many, many levels beyond their nominal item level. It’s about the relevant stats and bonuses, rarely about stuff like absolute physical DPS.
Sockets, as I’m learning, are crucial. Not just number, but links and colors. You can indeed craft your way around some blockages like not the right color, not enough sockets, not the right links, but it’s expensive and hit or miss. Always be on the lookout for the links, colors, and numbers of sockets you need.
Eventually, can’t recall when, you get an ability call Desecrate, which casts an AoE damage area on the ground which also spawns three corpses (I think it’s three). You can them summon them as Zombies. Handy. Also, use the spell totem + summon skeletons trick. Very handy.
And yeah, it’s a very cool game even for putzes like me.