1005 water changes, hmm, thats alot, u mean 100% lol.
Just get a gravel siphon, trust me its worth it. I dont like divided tanks though, they stress out the fishies.
I do agree, a marble would be awesome. I suggest a filter, and as long as you keep up your water changes, you can o a fish in cycle. Don't worry about quarantining, who else is he gunna get sick? :) Just wait a bit before addign decorations.
basically,heres wut u need
undivided, 3+ gallons
anything goes. make sure it doesnt leech color
Live or silk. no sharp edges that can tear betta's delecate fins. If it can rip tissue paper, or snag panty hose, its too sharp.
(betta safe) decor
same rules apply, no sharp. If it leeches color, remove it and the fish immediately
rated for your tank size
ratted for your tank size
(food) I use ttramin tropical crisps (great for community tanks and small fish)