Most gobies match up with specific pistol shrimp. For instance, I have a pink spotted shrimp goby and a tiger pistol, they have never ever met. lol They didnt match up at all.
I am looking to get a candycane pistol and another goby. The pistol shrimp that match up with the most gobies are alpheus , I think thats how it spelled... Do a little digging on the internet and see which ones match up that you like.
And yes, wait at least 2 more weeks before adding the pistol/goby pair. The two fish you are adding this time will force your filtration to adjust so just keep an eye on parameters. From what I have seen on this forum over the years is that most fish die or have issues when they are the first fish going into a new system instead of adding a fish here and there after the tank has been up for a while. But if you go slow and watch whats going on I dont see why you wont do really well.
Good luck, post some pictures when your first batch of fish come in.