[gills]

Step 1. Learn <some activity>.

Step 2. Perform <some activity> in return for cash.

Step 3. Purchase chair of dreams.

At any rate, your parents aren't the answer.

I know this will probably enrage some ergonomics hacker, but I actually prefer wood chairs with straight backs over anything fancy (I sit up straight even in nice chairs, so there doesn't seem to be too much benefit...). You could get one at goodwill (or similar) or a restaurant supply store for a few bucks.

Don't sit on the ground or the couch for long periods, though. You could damage your spine. Some people like standing desks too, have you given that a try? Maybe it would work long enough to earn the money for your chair.