I am 14 and I have wanted a fish tank for a couple years. Recently I have been saving my allowance drulling at the fact of owning a fancy smancy windows mobile pda. Dell axiem...

But anyway I have this fish tank (no filter, heater, gravel, etc.... Just a tank I made it into a terrarium after I had a plant phase and wanted to keep carnivorus plants. in it so i set that up and I got this unknown tropical plant and it just grew and it choked my poor venus fly trap and other things of water. Its still alive after not being watered for about 2 years now and its a rain forest plant 0__o. Now onto the point I was thinking of finally ripping that plant out and turning that aquarium actually into an aqurium. So i goto this little pet shop up the street called all about pets. And I ask what Ill need because I looked on the internet and found some cool fresh water tiny fish to fit in my 12 gallon tank and I wanted to see what the store had. After totaling the caust It came to arround $80 to $90 dollars not counting what I paid for the tank. So now im torned between the cool fancy guppies and my flashy pda. I have always gawked at aquariums wishing I owned one. I talked to my friend and asked him how much he enjoyed his tank He said for the first couple weeks it was cool but now its just a ho hum fish. So I have 2 questions.
1 is that price too much should I hit a chain like pets mart or the Mejier pets department?
2. Is it worth my time do they get old and boring or will I seem to like them Like I like other peoples tanks all the time?