dog - great keyword
dogs - good keyword
supply - good keyword
stuff - random and generic
store - great keyword
tobuy - unaesthetic term
Sorry mate, but it's looking like a very patchwork-ish domain, trying to combine as many keywords as possible. A good domain name is centered to its topic. If you were an expert in this niche and therefore a potential buyer, would you buy it yourself?
You may always ask yourself this before registering a name. Cheers and best of luck nonetheless!