Converting triple crank to single or double
At the simplest level you may simply be able to unbolt a chainring and re-set the limit screws on the front derailleur to stop it shifting onto the missing chainring. I assume you're trying to remove the smallest chainring, and those are fairly commonly removable even on cheaper setups. Slightly more expensive setups will have all chainrings removable, so you could remove two chainrings.

If you can't do that it's probable that your bike is so cheap that buying parts for it is a waste of money - while you can buy cheap parts the markup and distribution costs mean you're not saving much over the cost of a better part. But spending $100 on a new crankset for a $300 bike doesn't usually make sense.

What you will probably find is that even with a single chainring you still need the front derailleur to stop the chain falling off. Derailleur systems are designed in many ways to facilitate that, only they call it "changing gear". If you look at many of the 1xN setups on the market they have a chain retention device that does the same thing.

If you just want to find out whether you can deal with only having one chainring, I suggest simply not shifting gears on the front derailleur. See how you go, if you regularly find yourself having to either shift it or get off the bike, a single chainring setup will probably not work for you.