Don't even attempt to make an op wizard build until level99 and floor 200+. For now, just get what you can and grab things that seem stronger. You dont have enough crystal to make even 1 pure craft build so just grab what you can and save up as many crystal/mythstone as possible. Also gold.
Some things to look out for: Aftermath set, reactor set, plagued set, druidic set, electrified set, cosmic power set builds and other raw legends that you pick up.
When you get enough crystals at a high level, do try to get maxed farm affixes. Only do this when you have a big supply of crystals. For now if you want to farm better, just look out for random items with farming affixes, spend all 20 hero points on the fortune skill and find a way to survive easily.
If you find mythic 3 too difficult, go down lower and farm/conquer there.
These crystals are extremely powerful later on so its worth saving up as many as you possibly can.
A good legend to aid you with farming as a beginner is the steigers fortune and other good things like that. If you have rogue, buccaneer gears are also good.
What im saying is that farming is the biggest priority at your level whether it's gold, items, crystals/mythstones and exp. Try to reach floor 100+, that's where more powerful items are located. Do your best at building up your character to be the strongest possible person you can get without spending too many crystals and save up as many crystals, especially high rarity crystals from jasper-obsidian and even rare crystals from emerald-amber as well as normal rarity crystals calcite-diamond. Angelite is worth using to try and get the affix you want at your level when you have enough.
Still if you are going for the dmg, get legends or items with weapon dmg and even element dmg+ (it shows up as poison dmg+, shock dmg+, fire dmg+, etc for each element). If you get the druidic set and have the wildhide robe, it has ignore resist. That affix is extremely powerful for dmg and makes defeating enemies so much easier and your elements attack at full potential as well.
I hope you understand what I am saying and thanks for reading.
If that was TLDR: Just farm, look out for good affixes on legends depending on a certain floor and try to get higher dps as you rise higher through the floors.