Go with a refillable tank. I work with cylinder gases, and not only is it a pain to dispose of a disposable tank, it's rather costly in the end to essentially purchase a new tank each time. On top of that, most disposable tanks are rather small and won't last you very long.
Seems like a bit of an investment, but get the largest co2 cylinder you can practically store. If you can store a 20#, do that, but for me I went with a 5# because a 10# just barely won't fit in my stand. I just got it, so I don't have a lot of info on how long it will last, however most people refill about every 6 months or a year.
The bubble rate is very specific to your tank. I know a guy with a 75g that's pushing 10 bubbles a second(he took a picture, counted the bubbles, and divided by the shudder speed). Get a drop checker and start out small, 1 bubble per second or something, then up it according to the drop checker.
And just in case, a drop checker is a nice little gadget that inexpensively allows you to measure the amount of co2 in your tank. Do a thread search on drop checkers to find out more info, there have been multiple threads about them.