PREFACE: I am a low elo player. However, I OTP'd Tahm Kench mid from Bronze IV to Gold IV in approx. 3.5 weeks playing this. There is massive potential for optimisation with build, runes and macro, but this is just based on my personal experience and what works best for me.

Happy Unbenching

focus entirely on farming minions and staying alive until you have your first back and item. Tahm is not entirely CS dependant and spikes for duel potential inevitably as long as you do not die.

After First recall, bait out opponents CC, if any and use W to dive in and trade, ideally 3 stacks and Q to stun. Retreat and allow second wind to kick in and repeat.

Maintaining this pattern allows you to become near unkillable without jgl assistance and at minimum you stonewall their midlane and best case you stomp.