You saying he only knows Mike is not true at all. The only thing missing right now is him regaining his lawyer practice license. He knows Mike, of course, but he also knows Nacho, he even knows about Tuco. He has Huell as his security already. His secretary (I forgot her name) is already set once he goes back into law, and all he been doing is selling and making connections with CRIMINALS. The criminals he deals with even know him as SAUL. He even give them cards that say "Better Call Saul" on them. So, the transformation from what he's doing now to being a "criminal" lawyer is basically SET because those same people he been selling phones to are now his valuable customers who they can trust. Literally the only thing missing his him getting his lawyer practice back. He's Saul already.
If you was expecting or assuming he would be involved with Gus' world, then you going to be disappointed because in Breaking Bad he never MET GUS. He never was involved in that only until Walter White, and that's how Saul referring to get with Mike to make the connection with Gus, because Saul can't.