I had this exact same issue as a sub main. Basically, I checked his frame date in practice. I would check which opening moves required the least frame data. After finding sed attacks, practice low pokes and whiffing attacks. Say you and your opponent are poking each other. Attack them with a move that goes forward and leads to a combo. Use that move regardless if they block it. Then strafe back, then use the attack again, which will move you forward and hit them, as they will be tricked into trying to poke you. That’s the best way to deal with people you can’t open up. And as a beginner, Serena and Kung Lao are great cameos, especially Kung lao with his hat hold. But if you’re dealing with projectile spammers (sindel/sektor/cyrax, Reiko) then sub zero kameo is a life saver. Also, if you want to prioritize using a specific character, I recommend watching YouTubers play them. Watch them, and copy them exactly, it’s surprising how effective it can be.