Test realm to try out builds with Gear/Items/Skills/Trees?

Hey I was just wondering as I did not find any answers with searches in the forums or in search engines, is there a test realm that I can go to and pick unique items, gear, gems, skills, classes and try out the build and see how it plays against target dummies?

Like a realm that has all uniques in a chest to grab instantly for free just to test with, all skill points, level 100 ect. all skill gems that I can plug in and then run around testing out the build?
It is really hard to learn this game with hundreds of uniques that I have never seen and don't know what they do or how they work, skills, abilities in trees without actually owning the items in game and seeing how they work.

It feels like the only way to make a build is to run one from someone who has tried every unique and has them all memorized, who knows all the classes, skill trees, gems etc. by heart and can theory craft with them.

Other games you get a unique and it boosts your build, in POE you get a unique and you need to respec the entire build because now you are using you life to turn chaos into a mana eldritch block but it converts evasion to flasks and then after the flask is empty a spirit skeleton comes out of your offhand and drops a consecrated orb which divides. And that's only your boots. Oh did you have the shaper version? Ok now the consecrated orb is a shadow veil of hate lightning smoke! You need to change your tree to X/Y/Z. What? You didn't know that? Wow do you even own every unique in the game on every level 100 toon?

How do I test all this stuff out without buying/dropping every unique item in the game and then building with it from a massive 100 bagslot inventory in standard and having one of every character leveled to 100 with 500 orbs of regret?

How the hell do you even begin to theory craft without memorizing all items/gems/trees?

Or should I pretty much just go with the notion that "My build will be crap anyway".

nop

We have test realm - Sentinel league, except the part with the all items available.

nope...our test realms are the new leagues...especially the first month.

Its called Standard.. Can even test items that are no longer in the game.