Where to start with oil paints, what colours do you need? How do you know the differences between the different makes? There is so much you can learn but a bit of the basic lore may help.
All oil paints are manufacturered from pigments, a binder (a type of oil) and in the more student quality paints a filler. Hence the professional and artist quality paints have the best quality pigments, best quality binders and none or a tiny amount of filler. They are more powerful colours and mix together successfully to clear strong secondary colours. Student quality paints have more filler which dilutes the strength of the pigment and when you come to mix the colours the strength of the secondary colours is less true.
The choice of colours is very personal, as a quide a starter set should consist of two yellows - lemon yellow and a stronger cadmium or equivalent; two reds - cadmium red or an equivalent bright red plus an alizarin, madder or cadmium deep red; two blues - cobalt blue and ultramarine (landscape artists like Cerulean for the sky); a few earth colours - yellow ochre, raw umber, burnt sienna and the stronger white Titanium. Greens can be mixed but Terre Verte is useful for landscape and portrait artists.