Before you make any decisions, read this article by Thom Hogan.
http://www.bythom.com/support.htm
There are three parts to a system - legs, head, and plates.
For plates, go with the generic Arca Swiss plates. These are the standard across the industry and will keep you from having to replace plates as part of future changes. Stay away from proprietary plates that lock you into a specific brand. There are lots of companies that make Arca Swiss style plates for your camera body and long lenses. If you buy a camera plate that is specific to your camera, the fit is better and it tends not to work its way loose - but it is more expensive than a generic plate. On a budget you could start with just a flat generic plate to attach your camera to your ballhead, but you might want a camera specific plate later.
The tripod head makes a big difference in your satisfaction with your gear. A good ballhead is expensive - but its a buy it once item. In the US, a good ballhead runs $325-400. I have been using Really Right Stuff BH-55 ballhead since my first ballhead. They are well made and worth the added cost. The Markins ballheads are a good value - I like the Q10. And there are others like Arca Swiss that make good ballheads. Good ballheads maintain their value - if you ever want to sell it you can probably get 70-80% of your purchase price.
https://www.photoproshop.com/product_info.php/manufacturers_id/10/products_id/28/language/en
Tripod legs are also important. To a large extent its one of those cases where you get what you pay for. You want a tripod that supports plenty of weight - well over your current gear. I'd look for something that holds 15-25 pounds. Gitzo 3 series carbon fiber tripods are the standard by which others are measured. If you need to save money, aluminum legs are a lot cheaper - 35% lower in the Gitzo line. And there are some other good brands that save money. I like the Feisol line, and Induro makes some good tripods. Manfrotto is an option but they also have a number of cheap tripods. Something like the Manfrotto 055XPROB is not too expensive and probably adequate for your needs. The Manfrotto runs $190 US and is on sale for $155. The Feisol and Induro 3 series CF equivalents run $400-450 US - about 2/3 their Gitzo counterparts. Like ballheads, tripods have good resale value.
If you are going to save money and possibly upgrade later, spend what it takes on a good ballhead and cut corners a little on legs. I know this is going a little beyond your budget - but read the article from Thom Hogan again.
