Don't buy more tools than you'll ever need. As kenny mac says, buy a decent set & build up from there. It's better to buy a basic set of quality tools than a shed-load of poor-quality stuff. "150-piece" or whatever may sound good, but in reality you'll probably only use ten or so regularly; for example, such a set may contain A/F sockets, which you don't need for modern cars.
If I were starting again I'd buy a 3/8" socket set rather than 1/2". I'd also consider "Metrinch" or similar flank-drive sockets - they won't round off the corners of stubborn fasteners like normal sockets will. (Not that I've ever used them!)
As for quality, unless you can actually see before buying, steer clear of "own-brand" stuff like Sealey & Clarke. They have some very good stuff but as they buy in from different manufacturers their quality is variable. Halfords own-brand stuff is very good.
Where are we going & why am I in this handcart?