duncanvr,
As almost all comments said already you are not going to be the only dealer looking for bargains in order to re-sell, and I guess you already know that

I have few advices - and please forgive me if I say the obvious:
1) Don't rush and spend these $2000.
2) Start selling whatever you already have and see how the market responds. You might be surprised to learn that what you consider to be a "good seller" doesn't sell at all, and what you might consider to be a "no seller" sells very quickly and for a profit. Only after you gain understanding of the real (as opposed to the supposed) behaviour of your market start spending the rest of your cash.
3) Online selling has it challenges. You must add new items on a regular basis and let your already existing buyers (and you'll have those of-course) know about new items in your store. Repeat business is the bedrock on which every online business builds itself.
4) There are strong months and weak ones. You will gain understanding of the seasonal nature of the trade only after a year or so of selling. Until than, any conclusions deriving from good/bad sales are wrong.
4a) It is a seasonal market and since you have mentioned the different
ebay sites on another thread I would suggest you wait for your US and European material to be listed on the relevant
ebay sites during their winter and do the same with your Aussie and NZ stamps on your winter.
5)
ebay is where sellers "harvest" email addresses. After your inventory grows you might want to consider moving it to cheaper venues (delcampe and such) and let your buyers know where to find it. As you already know
ebay charge like a wounded bull and if your profit margins are thin you will end up with no profit at all selling only through
ebay.
I could go on and on and on....
To sum things up. Give yourself a year keep on listing and refresh your inventory on a weekly basis, buy after gaining understanding of what sells (where and when) and be patient - you can and will build loyal clientele which will keep coming back to purchase more stamps.
GOOD LUCK !!