>>2017848
You're in, welcome aboard.

Remember to conserve all the roll tickets you get for being a new player (100 to start, 100 upon reaching each rank tier, 350 from the Research Notebook, etc)
The gacha rates are shit, but you can guarantee whatever character you want if you roll enough times. But rolls don't carry over between banners, so the optimal tech is to save up 2000 tickets and then blow through them (hopefully not all of them if luck favors you, but potentially all of them) on a single banner.
If you save from the start, you can reach 2000 tickets within a single season.

Hero crystals are the premium currency, and you can get them for free from in-game events. Your first priority with those should be securing the pro license (battle pass) since it pays for itself. Any excess crystals you have after that can be devoted to the premium login bonus.
You can use hero crystals to roll in the gacha, but it's awful value. Do not EVER use hero crystals for tuning, it's absolutely abysmal value.

You should look into the MHUR x MHUI collab event that's going on right now. Not just the in-game MHUR missions, but if you download My Hero Ultra Impact (the phone app) and link your accounts, you can complete missions in that to receive quite a lot of additional character data in MHUR, which will give you a bigger head start on tuning. It only takes a few hours to complete basically all of those missions in MHUI.