For someone that is just starting to breed I wouldn't recommend breeding any male that is under 6-700 grams atleast. They can and will breed when smaller, but if they go off feed it doesn't take much for a 4-500 gram male to end up in bad shape pretty quickly when breeding. Breeding is alot of work and stress on the males.
As far as what to breed him to, if he really is a Dinker then for me it would completely depend on what he looks like. So pics of him would help us point you in the right direction as far as possible pairings go.