Hello!!! I am mostly micro cash game player, but I was wondering if I can take a shot at some tournaments once in a while. I know that good bankroll for tournaments is 150+ buy ins, but is there a rule if I play only one or two tournaments durring the big online series (SCOOP, WCOOP etc.)

BRM is not a general rule, it's something you decide for yourself that prevents you from going broke
if you have sufficient income from another source (like cash games) there's no need for a tournament bankroll

150 BI's is not a good bankroll
especially in the big online series, very good players go on 1000 BI downswings because the variance is HUGE
you're most likely not that good, so your possible downswings can be bigger.

on the other hand if you play slow structures and small fields you can go with a much smaller bankroll

like everything in poker, it depends

That sounds more like a budget rather than a bankroll

Bankroll management depends on your goals. If your goal is to provide a sustainable living then yes, a large bankroll is necessary to overcome downswings, especially in tourneys. Since you are a micro cash player I doubt you are doing this for a living.

If your goal is to grow a bankroll and climb stakes then you can be more aggressive. This seems more like your situation. At least with cash games.

And if you are just looking to play a couple big field tourneys and take a shot and have fun there is nothing wrong with a poker budget instead of a bankroll.

Story time: I was grinding cash games in school from like 2009-2014 or so. I started with a $100 deposit (well my final $100 deposit lol I was already down like $2k at that time) and played 10nl until I had $250 and took shots at 25nl. If you lose a few buy ins drop back down. Eventually I climbed up to 200nl and 400nl+ all the while using this aggressive bankroll strategy.

I occasionally played tournaments during this time. Though all of my major bankroll leaps came off the back of nice scores, I mostly considered my tourney buyins to be budgeted off my cash game profits. Make a few hundred one week playing 100nl, enter the $109 bi $100k guarantee that Sunday.

It was a win in a $1 tourney for ~$250 like helped me cement myself in 25nl. There was a $15 tourney for a ~$3500 score that cemented me in 50nl-100nl. There was a 6 month period where I finished 3rd, 7th, 1st, and 2nd in Sunday $109 100k guarantee combining for almost 50k. That run cemented me as a mid stakes player until I stopped grinding online cash around 2015 to start a career.

Even as recently as mid 2018, I was between jobs with $10k bankroll and $10k living expenses and decided to travel around the WSOP Circuit for a few months to take a shot, knowing it wasn't sustainable and that I would probably go bust and be back at a desk job within a year.

It was heading down that path with just enough to play the $1700 Main Event at one of the last stops in 2018. I am pretty sure no one would say that dropping your last $1700 in one tourney is a good idea, but I ended up winning the whole thing for ~$125k. This allowed me to fund my Circuit journey for another year and I had a full WSOP experience that summer, including my first Main Event. (It was a horrible summer results wise, but a great experience). Now I am back at my career and play tourneys on the weekends when I can.

TLDR- Sorry I got into story time a bit there. Be aggressive with your bankroll as a micro stakes player. Dont be afraid to take shots. Don't be afraid to budget out money from your cash game profits to take shots in bigger tourneys that you dont necessarily have the bankroll for.