Firstly, the Gacha golds are just better than the event girls in terms of stats and abilities. So , I would advise you to priorities Gacha golds over event girls.

Next, you should go for girls who are currently bloomed. If you are new you won't be blooming for a while, but it's good to make sure the girls you're investing resources into are are able to bloom. A full list of girls who can bloom can be found here. We get a new batch of blooms every maintenance, so keep an eye out for if a girl you have gets one. Every gold will have a bloom eventually, so if you really like a gold who can't currently bloom, she'll have it at some point. However, it will require some waiting.

Finally, between the girls who can be bloomed, just choose a waifu or a girl with abilities that you like.

There's not really a tier-list for golds, they're all good enough to have a spot on your team (once they're bloomed anyway). However, you can always post which golds you have here or on the FKG Discord and people can recommend you which girls to prioritize. There's a small number of golds are a bit better than the others, but there isn't that much of a difference.