OK, so some things to look out for. Make sure you're ordering the seatpost of the right diameter. Best way to figure this out is to measure the one you have currently. Also make sure that your new seatpost is long enough so that you can ride with the seat as high as you like it!

At the end of the day seatposts usually are bad for three reasons:

1) They're heavy
2) They slip inside the seat tube.
3) The interface for attaching the saddle to the seatpost sucks.

You probably don't care about (1) if you're on a budget. Recommending a seatpost that doesn't slip and has a good saddle attachment mechanism is a matter of looking at reviews. Kalloy used to make good cheap seatposts, but they seem to have disappeared off the market. Not sure what other brands at a low price point are any good, sorry!

Most setback seatposts give you a setback between 10 and 25mm. As you "want to try it out", pick one in the middle I guess!