Im feeling extremely discouraged

Ive recently had 4 female betta fish deaths in the last 2 months. The first 2 died because I ended up doing a lot of fish research after getting them and another one. Well i learned about needing to clean substrate and the water collum so i naturally bought a siphon. I have a 10 gal (i didnt know the tank requirements for a betta, especially not for 3 females) and cleaned half of the gravel in one go. Then i learned about the nitrate cycle.. the hard way... i released so much ammonia in the water and got nitrate levels to over 200 which by the time i noticed, they were aleready beyond healing... so they passed.

I had 1 remaining female and impulse bought a twin. Well... she came with parasites that then passed on to my survivor. Resulting in them both dying.

I was gonna get a 30 gallon when the money came in but now im debating the whole thing.

Tldr; 4 dead betta fish in 2 months because i didn't think far enough ahead.