I use Oster A5 clippers. No. 10 blade for head and top of ears. No. 7 or 7f for body. Depends how short you want the coat No.5 or 5f leaves coat longer and more natural looking.But think if I was to replace them I'd buy the Andis ones they come with one blade so tend to be better value for money and from what I've heard they are very good
Cheaper ones will do the Job but you soon notice the difference, they tend to be heavier and noisier and I don't think you get as good a finish with them.
It's the same old saying, you do get what you pay for, if you think of how much they cost for a good pair and the saving you make by doing it yourself they are well worth paying that bit extra, I would go for Andis.