I always preferred knockhill in the rain. Less grip - more fun - less tyre damage.
I'm no pro, done a couple of SIDC days and a couple of trackscotland days there.
It doesn't matter if you are the fastest or the slowest, what matters is the fun you have out there.
You'll probably find the first couple of laps a bit daunting and there are rules on overtaking (not in corners, nor under braking and only in the three straights) as Chris says, be aware if those around you and if someone's caught you up, you just indicate right, pull over to the right (lifting off is optional )
I'd say definitely get down to the trackdays that are organised here, go speak to as many folk as possible and get pax laps in different cars as well as going out yourself.
At most days there is an instructor who will be happy to go out with you and give you pointers on lines, braking and your technique.