Home Depot sells water based polyurethane; "silver" label can, I think it's "Minwax" brand; could be about $ 30.00 / gallon; use it all the time; excellent results. We use "satin"; gives excellent shine.
Remember: 1) buy a good applicator (lambs wool) and stick for it; if you're cheap, you won't know what you did wrong until the job is done; then it's too late ! 2) read the instructions, again, read the instructions ! 3) look at some of the home improvement sites, including Loews, they give instructions, print them out. 3) water based poly doesn't usually "yellow" over time; oil based poly does, but oil based poly lasts longer. 4) you can't just put poly on the floor; there is a method you must follow; wood has to be "screened" first, otherwise, the dried poly will peal off like a banana peel !
One more....buy a good face mask; don't inhale the vapors, they might do damage to yer innards....who was it (Clinton, who said "I didn't inhale !!")
Good luck !!