I used to be into tractor pulling and have hooked to the sled many,many times. There are just too many variables to tell you for sure what gear you need.
One of the main variables is track conditions. Watch the pullers before you, if they are getting a good bite then you may want to go in low 1st. If the track conditions are bad and the track is getting loose you may want to try low 2nd or high 1st. Reading the track is almost as important as what vehicle you are using. If you watch the other experienced pullers you can see them paying close attention to the track conditions, which can change in just a few minutes time.
Another big variable is the sled. Some sleds will suck hp more than others depending on the construction of the sled and and the length of the hook chain. The shorter the chain, more of the sled weight will be transferred to the deuce, giving you more traction and sucking hp.
If you're lucky, there will be other deuces that pull before you and you can watch them to see what they do. Most of all, just go out there and have fun.