What modelling tools do I need to get started?

Most modellers have an extensive tool kit, a tool for every eventuality.

But when first starting a scalpel or a decent craft knife will suffice.

And a selection of different size paint brushes. Paint brushes go from the larger size 7 down to 00000

You could get away with painting a basic model kit using two or three brushes Size 5 or 6 for larger areas, Size 2 or 3 for smaller areas and Size 000 for detailing such as faces, eyes etc.