I was impressed with a friend of mine throwing a Detour for medium oiled lanes, had a nice arc to the pocket. Myself, I love my Eraser Pearl Particle from Storm for medium/heavy to medium conditions, it's matched up well on short and long oil conditions.
I hear what you are saying about not wanting to spend a ton of money on a big arsenal- if you bowl mostly in the same houses, I would say a medium/heavy ball, a medium ball and a light oil ball should be enough for you.
Matt