Welcome! This is an online support group for anyone who is very afraid of dentistry or who suffers with dental phobia. Please note that this is NOT a general dental forum! You can find a list of them here.
Cant comment about whether to get lowers before uppers if you need to get them. But what I can say is that with uppers, the suction is much better. Your dentist should give you ample opportunity to get your 'bite' right and will adjust as necessary - involves a lot of face pulling lol - but try not to build it into something that is impossible, because it isnt - will take time - all a bit alien at first, but certainly doable.
I just want to second what Kim says, mine is only a partial and was a bit trickier than the uppers but better than a mouthful of horribly unhealthy teeth, don't Expect it will be spot on but don't expect the worst either, go with it take each day and each step at a time, they will never be as good as real teeth but they can get pretty close, and I don't regret having mine done and apart from chewing sticky toffee nothing is out of bounds now
' a bad day with good teeth far outweighs a good day with bad teeth' Wishing you well xx