In reply to tommyd_747:
Sport and trad are quite different disciplines and really you want different ropes for them.
When sport climbing, you want a single rope, you fall or rest a lot (or most people do), so the last few metres of rope get destroyed and you trim them off repeatedly till your 80m rope is more like a 50m rope. So if you're going to do a lot of sport climbing, especially if working a hard route rather than always trying to on sight, you want an 80m single rope. If you are starting out, just look for a good deal and don't worry about expensive ropes dry treating, triple rating, etc.
When trad climbing, it is, in my opinion, important to get used to using half ropes, so you want a set of two half ropes that are either 50m or 60m long. Most people I know don't trash their half ropes in the same way they trash sport ropes, so they should last longer, but again if you are just starting out, I would just look for a good deal on something cheap and later on you can look at saving up for more expensive options.
Probably not what you want to hear but I would recommend different ropes for different disciplines. If you are completely cash-strapped, get a cheap deal on a single rope but if it is a shorter one (e.g. 50m) be aware of the length and always tie a knot in the end when abseiling or lowering. And consider your trad lines carefully - if the gear is spread out all over the place, pass the route over unless you have access to a partners half ropes.