I'd suggest with staying at 5 gallon batches and just making different beers so that you can try different styles to see what you truly love before committing to brewing 10 gallons of one beer, because if you wanted to test a different style with a 10 gallon system you might have trouble with the submersion of all the grain of a 5 gallon batch in a 10 gallon batch system (if that makes any sense to you lol).
BUT, if you know what you like, and I'm assuming you'll keep your 5 gallon system - you won't have this problem.
If you only had $1000 to spend I'd get a quality kettle, a propane burner, and a quality BIAB bag.
1. BrewBuilt Kettle 22g - $429.99 (MoreBeer)
2. Bayou Classic Propane Burner - ~$50 (Amazon)
3. Propane Tank - ~$50 (Any refill place near you - my CVS refills these - I think its $50 initial, $25 each refill... each tank for my 5 gallon batches lasts around 5+ batches I'm just under estimating because I've never really counted)
4. Quality BIAB Bag - ~$30 (wilserbrewer BIAB Bags - makes the best damn bags on the market. He'll make a custom bag for you, add in hop bags, and a pulley system, all for under $40)
+
5. Fridge w/ temp control
6. Plastic Buckers/Fermenting Vessels
There you go bud. Way less than $1000.
With the extra cash I'd go ahead and buy a nice long chest freezer and make a cool serving fridge, along with another fermenting fridge so you have something always on its way to a keg. Craigslist, or LetGo is always a good place to find people selling freezers.
PS. I've always contemplated going full electric due to its ease of use and less cleanup, but honestly, I love my brew day and have no problem with washing dishes... I work in a fire house with sometimes over 10+ people so washing dishes is pretty much my side hobby. Propane is pretty cheap, and heats your stuff up way faster than electric anyways.