I'll choose the same way I choose anything: Process Of Elimination.
First off, this is an island and we're here as a group. Despite us all being assholes online, I know gamers well enough to know that you guys probably aren't going to go around killing each other. From the original description, it seems that there is no actual threats on the island. So Hell Rider and Mr. Pepper and Womba Womba are eliminated because I don't have any enemies I need to kill.
Blinky, Bones, and Rolf are relatively useless, so they're out as well.
We're on an island with a bunch of gamers, and while I'm sure some of you have herpes most of you don't live in enough of a bad place to be carriers of any serious disease. Thus, Cantelo is out as well.
Despite being a lamia and thus sexy, I would rather not be near something that might kill me with its saliva just because I smell nice. So COily is gone too.
That leaves Mildred, Gilligan, Murray, Boleslava, and Kazoo. All of them to various degrees can provide vital supplies in the form of food and/or water. However, Mildred does this better than the rest of them. His only disadvantage is that he does not like me, which can be easily solved by having Boleslava remove that thought. Thus, the ideal ones to bring are Mildred for infinite wealth and Boleslava to keep Mildred content and tranquil.
tl;dr: Mildred and Boleslava
>with some corrections due to personal name confusion