My KJ came with every skid except for the one for the transmission and I can tell you that even after I put on the transmission skid my gas tank skid was still the last to get a scratch on it. The one that has the most scratches is the motor skid so if you don't have that then you should absolutely get that first. If you can afford to get all the OEM skids then go for it. They've suited me well but if you plan on doing a lot of hard trails then you may want to look into tougher armor from a place like All J Products (boulderbars.com). In any case, my vote for what order to get the skids would be engine, tranny, then gas. Don't forget the rock rails to protect the sides of the Jeep.