spending your money on atleast a 5gallon tank (even better a 7-10gallon) for a few bucks off craigslist.com ( that is if you can afford it and the space )
doing alittle research on a suitable gravel,sand, or plant substrate ( whichever fits your needs best )
investing in a small filter
let your tank run for 3-4 weeks (average) to "cycle"
if your doing "live plants" follow instructions below, if not i would recommend NOT using plastic plants because of the threat of tearing your bettas fins, go with silk plants ( theyre alittle more expensive, but if your going "fake plants" this is your best option, they even look more realistic)
get a 10-15 watt (full spectrum would be ideal) bulb
getting a bottle of API leafzone fertilizer, or something of the sort is benefitial
there are many different plants that would work, however in a bowl, i dont think they'd do the best, as well as your fish. liveaquaria.com is a decent site to check out plant types and names ( it includes pictures ) then doing alittle research on the web of their needs, even posting some of your plant ideas on here, im sure someone would be happy to help eliminate whats best and whats something to reconsider..