Very good advice was already given above, and I'll just add my 2 cents.
As HoneyCrush said, the BRM for Tournaments is around 100 x BI (buy-in) for players who want to make serious money, or 50 x BI for players more on the recreational side who don't care if they lose.
Meanwhile, because Cash Games have less variance, there's really no limit set upon the Buy-Ins that I've heard off. Here's how a pro chooses Cash Games: he turns his tracker on and goes around the tables. He is looking for a table where 1 or + players are huge fish, calling huge amounts of hands without being aggressive and not folding much.
He will then sit down. Usually there will be at least 2 other professional players that are stacking off that player. What happens when that fish leaves? The pros leave too. GG WP, cya next time. They won't play each other.
In Tournaments you don't have this freedom. You can't choose tables, you can't choose players. You can't even have solid reads on the players at your table (assuming they are Unknown) because you'll switch tables frequently. And if everything is going bad and you are losing chips because the other players are outskilling you, you can't leave the table and find someone worse than you.
Besides, in tournaments, there's a lot to worry about
: how many BBs you have, ICM, all the different phases, comparing stacks constantly, etc. Cash Games are much more basic than that. As long as you have a fair understanding of odds
and (at High Stakes) ranges, and have a good basic basis on theory, you're golden. There's not too much detail to worry about.
I'd recommend you try Cash first. Or at least STT (Single Table Tournaments, usually 6-10 players). I started out with cash and found it quite enjoyable. Although I've burned through a $20 bankroll as well (with aid of Spin & Gos too to be fair). Besides, the part I like the most is that Cash Games are faster. If you go on tilt, you can just leave. And if you win, you win instantly. You can say "I'll leave after I win $5 so I don't get too excited, and I'll leave after I lose 1 or 2 Buy-Ins so I don't get on tilt" and you can follow through. There's no need to worry about getting in the prizes and rebuys and stuff. Much easier, IMO.
Good luck at the tables!!