for nearly a 30 gallon you could get a couple of fantail types and maybe a couple of dojos.
you will need 10 times filtration to keep the tank healthy and clean as they are really messy fish and as for decoration then thats up to you, just be careful you dont get anything the fish can get stuck in or behind. gravel should be pea sized and a lot of people prefer to go with nothing as this will stop the bad bacteria from building up. if you go with nothing then a few river rocks and a small handfull of gravel looks nice. any plants you might want can go in to small plant pots or candle holders. the choice really is up to you.