i want one that comes with everything i need to start. I'm hoping to get a Betta if that makes any difference.

There are aquarium kits at Walmart. I bought my first 10 gallon there for $35. It comes with a filter, hood and light, starter pack of fish food and water conditioner.
Betta do not require air pumps, but if you want to add other fish you need one.
Gravel and decorations are separate. 2 small bags should do fine.
Bettas like hiding places.

For a new owner i would say stick to around 10 to 20 gallon fish tank and keep a few small fish in there. If money is concern to you go with 5 gallon tank and a betta fish. Keep in mind fish keeping do cost money...can be a lot of money buying chemicals and fish and supplies. To spend less money you should keep your fish stress free so they wont get disease as easily which ends up you tossing them out of buying chemicals to cure but be aware the water may get infected. I bought a 14 gallon tank at petco Aqueon brand and i do recommend you buy Aqueon stuff over Top Fin which is popular and good too, your choice. There are many kits that different companies sells go to walmart or petsmart/petco and look around for one that suits you, don't get one any smaller then 2.5 gallon for a betta fish even that is too small i reccoment a 5 gallon tank (no bowl) make sure it has a top(your betta WILL jump out).

Bettas (Siamese Fighter Fish) are the most beautiful freshwater fish in the would, however the most abused. Contrary to popular belief, they don't do well in small bowls. The reason is that all fish need to have a filter, the betta is no difference. They come from the south coast of China and the surrounding countries, like Vietnam, Laos, Thailand, and Cambodia. Therefore, that makes them tropical fish, so a heater will also be needed. They thrive in temperatures in the low 80's. Siamese Fighter Fish live in the rice patties that are literally miles long, meaning that they do not "naturally" live in small spaces as most PETCO employee will say that they only need to be in small bowls. Get at least a 2.5 gallon with a sponge filter and a heater, of course 5-10 gallon is most definitely okay. Feed them food made for bettas, like Betta Banquet Premium Betta Food by Seachum or Hikari Betta Bio-Gold, these 2 brands are my bettas favorite. Even though they are tropical fish, do not feed them tropical fish food because bettas are carnivores and tropical fish food is made for omnivores. They hate flakes, however will eat them if raised on them. Feed only once a day, 2-3 pellets is enough, bettas have tiny stomachs, it's the size of one of it's eyes. Fast one day of the week, this is good for their digestive tract. Once or twice a week, feed them brine shrimp, bloodworms, mysis shrimp, krill, daphnia, atemia, and blanched peas (a high protein vegetable that help prevent SBS (swim bladder syndrome) which bettas are prone to. Use only silk plants as plastic ones can rip a betta's long flowing fins. pets question and answers,www.5d2d.com

GOOD LUCK!

me