Agree. If the Winton brand are for students give them a miss. Spend the extra money for the "Artist" quality, you won't regret it and they will last you for years.
Like others have noted, one tube will last a long time. You really don't use that much. I bought mine back around 1990 or so, and haven't run out of any of them yet.
Buy some liquine which will help the oils dry quicker and I would avoid using student grades as they tend to be more opaque and have cheaper pigments.
Start with the basic colours. When I start a new "large figure" I normally buy a specific colour to act as the base which I can darken and lighten accordingly. I.e. for Colonel Douglas of the 11th Hussars I just bought Prussian Blue and a Crimson for his strides. The Winton crimson (lake) was just too thin and difficult to work with.
As I mentioned liquine is s good medium to mix with your paints and they dry within 24hrs. I then Airbrush with s water based laquer to protect them and get the correct sheen.