In reply to Sempafi:
In 8mm dyneema I have a 240, two 120s, two 60s racked and two 60s in alpine draws.
Then I have in 20mm dyneema a 120 for abbing, and also a 60 and 120 in nylon which I sometimes take for 'tat' if there is a route I think the chance of retreating might be higher.
Finally I have a 21 foot cordlette.
Though this is quite a large selection used for alpine and trad. As a start I'd say a 240, 2x120 and 2x60 in 8mm dyneema (might as well start light or you'll only re-buy later) and then a wider 120 for rigging the belay and personal anchor for abbing.