Here are my quick opinions on your birds.
Welsummer - Type and color are not bad, tail angle is the biggest thing that stands out to me. I would also like to see her color darker overall.
Ameracauna - Not an Ameracauna, actually an Easter Egger. I would not show her at all.
Andalusian - The breed is actually Blue Andalusian. Looks to be a splash or a horribly colored blue. Since the breed is Blue Andalusian not Andalusian I would assume you would have to show her as a blue, not 100% sure and I will check on that. I have only ever seen or heard of Blues. However, I really like her type and her comb is surprisingly good. I would like to see a broader tail, slightly shorter back and better angle of her back.
Speckled Sussex - A hard breed to get correct with show quality birds. She has uneven speckling, and is posed weird(I know it can be a pain to pose them), so it is hard to tell type wise. I feel she could be broader in her body overall, with a longer back also. Overall she is not bad her mottling will kill her point wise though.
Black Shamo - I would not even consider taking her, the type is all wrong, I am questioning her even being a shamo. I am thinking she would possibly be DQed
Buff Brahma - Definitely my favorite, tail angle and back is all wrong. The markings actually aren't bad as long as you don't look around the feet. If you were to take any bird I would take her, could definitely see her doing ok.
Naked Neck - Wrong coloring to fit under any of the recognized colors. Type doesn't seem to bad. Personally I would go with a different bird just because of the color.
All in all if I were you I would take the Brahma and the Brahma only.
Just a small suggestion, just because you like a bird doesn't mean you should show it. My favorite bird is a LF White Cochin K I hatched out this year, however because he is a recessive gene from blue breeding his foot color is off and I know he won't place well in a show. So why waste the space and entry fee when I can take other birds who will do better. Especially for your first show. The less birds the less stress. Also have you ever attended an APA or ABA sanctioned show? If not I suggest just going to the show looking at the birds, watch the judging(from the next aisle over of course) and talking to people. Who knows you may buy some birds to show next year. It is better to learn stress free and know what to do and what will happen at the next show than to end up having a stressful time at the show and leading up to the show. You mentioned you wanted to gain experience, by watching and talking to people you will most likely gain more knowledge and experience than if you were to bring birds and show.