The minimum you want when starting out is an SDS and a combi drill, SDS should be 240v(110v for sitework) and 18v for the combi(in my opinion), 14.4v is generally weaker in my opinion - unless it's a good brand it may struggle with rad brackets or things like pan fittings.
When I started out I had a Black and Decker drill and a B&Q own brand 14.4v combi drill and they did me OK until I got better gear.
Combi just means it can do holes aswell as drive screws and will have more than one speed setting depending on which you are doing. It's not the best at either but will be fine for starting out. You'll probably move on to get an impact driver eventually for screws, it delivers all the torque to the head of the screw so powers them in better.
The SDS will be needed for small cores(up to about 40mm unless you pay a lot for it) and drilling through brick/masonry. If you're doing a lot of cores or doing the larger ones 3 or 4'' then you'll be wanting a core drill.
I love my Dewalt SDS, had it for about 10 years I think, but I go through combis every couple of years, maybe because I can never justify paying too much for them, I'm on a Ryobi 18v combi at the moment, not expensive at all but it does a good enough job.