Have a good horse that can work up the levels with you and a good trainer to support and teach you. Keep working and train at the higher levels until you feel confident enough to compete, just go for it!
My favorite place is my stable ^^ ahah, more seriously, I don't have a favorite place to compete.
The best advice I can give you is: before you go on big trials you have to have no problem on the smaller shows. If you still have lakes and you want to burn the stages, you will not enjoy yourself and you don't fluctuate !!
The second advice is to have a horse that can follow you in the competitions you wish to do.