If you want to start an adventure with oil painting, you will need a couple of things. Here is a list:
1. Oil paints
Oil paints are available in sets or in single tubes of various sizes (the typical ones are: 37ml, 60ml, 150ml, 200ml).
If you think seriously of oil painting and know that it will not be just something to try out, I advise you to buy oil paints in big, economical, 200ml tubes, which are much cheaper than the smaller ones. As you will use a lot of oil paint, the price is quite important, so bigger tubes make sense.