When you enroll you can order a kit or individual oils. The great thing about starting with a kit is that you waive the dōTERRA enrollment fee, and you get a the most basic oils for an even better price. The kits vary depending on the country you are enrolling from.
Of course you can also buy individual oils. You just need to add the $35 introductory packet to you order. The membership comes with a $25 renewal fee, for which you receive a free Peppermint Oil.
Here are some example kits:
10ml bottles of Lemon, Deep Blue, Breathe, DigestZen, On-Guard, Frankincense, Lavender, Tea Tree, Oregano, Peppermint + a diffuser and the dōTERRA essential oil Booklet
5ml bottles of Lemon, Deep Blue, Breathe, DigestZen, On-Guard, Frankincense, Lavender, Tea Tree, Oregano, Peppermint + Peppermint & On-Guard Beadlets and the dōTERRA essential oil Booklet