Lisa...that fighter is something else. I turned ,my conservatory into a Siamease fighter breeding project and ended up with more babies than i could cope with....one spawning gave me 200 babies which all made it to adulthood !!!!!
Tinkerbell, just to add that tropical fish are no harder than coldwater...infact due to the amount of waste and muck coldwater fish throw out, they need a much bigger filter system.
If you like the biorb, go for it. Not my thing but i know a lot of people who have them and love em. Just get the biggest you can.
As for fish, ideally you should go for a few bottom dwellers...maybe a trio of panda or peppered corydorus, some midwater swimmers....maybe a small group of tetras such as neons, lemon tetras or rummynose tetras, and a few for the upper levels such as a small group of white cloud mountain minnows or zebra danios. I'd then add a pair of platies or swordtails and maybe a pair of small honey gouramies. A small clown or bristle nose pleco or some otocinclus will help with any algea issues.
That's my suggestions. Avoid......Angel fish and other cichlids, as cute as they are, they will get too big and be aggressive. Guppies....not beginners fish anymore. Siamease fighters (often called Bettas)...will get ripped to pieces and can be nasty. Some barbs such as tiger barbs can be agressive as can some larger tetras such as serpae or red eyed tetras.
You'll make mistakes....my gawd i'm still making them after keeping fish for nearly 40 years but if you ask questions, you'll generally get good answers. Get a decent book, find a decent aquatic dealer and you'll be fine. Oh...regular maintenance once a week...water change, clean glass etc is essential...don't skimp on that part.
Good luck and keep asking