If you only plan on spending 30 dollars, eh... You will most likely get the fish, and gravel for that. Maybe the plant too. Youll be spending around 100 if you plan to actually put the fish somewhere it belongs, which would be at least a 10 gallon tank. Honestly, kits dont include heaters. Thats 15 dollars right there. The fish... theres not alot of fish under 1.50. And if you have a budget that small, This isnt going to work out at all.
How about this. You do some research on the fish to see what kind of fish you want, then look for some plants online to find out what could go with him. Then, look at the requirements for the fish and the plant. Then get a tank accordingly.
http://aqualandpetsplus.com/Betta,%20Basics.htm
Thats a page that will link you directly to the Betta fish. Its a very good beginner fish. You could fit him in a 2.5 gallon tank (not bowl) with heater, filter, and a small plant.
You might be able to do that setup for less than 30 dollars, but you might need around 40 or so for a 2.5 gallon with everything and a betta. And if you are going to spend that much, why not just go ahead and get a larger tank to get different fish?
http://aqualandpetsplus.com/Livebearer,%20Guppies.htm
http://aqualandpetsplus.com/Gourami,%20Paradise.htm
Theres some good beginner choices, but bear in mind, most fish need at least 10 gallons to be happy, many need alot more than that. That site gives you several choices in fish if you just want to browse around though.