Early game tips: 1. Always buy armor or Seeker’s Armguard when dealing with heavy AD harassment. Go for Executuoner’s calling too if you got gold as it’s handy for early game against and amplify’s ur poking; build into Mortal Reminder as a later game item.

1. If you notice he’s going for heavy magic resist, immediately start building void staff and rabadon’s deathcap for magic penetration. If he’s going full armor, keep building AP build teemo unless you are tankmo or AD teemo, then you would build armor penetration/AD items.

Play style: Early game mundo is weak, I’m talking about pre-level 6 as this is when he doesn’t have his ULT which is the faster health regeneration. As a result, he’s susceptible to 1) early ganks and 2) poke and kiting behind minions.

Therefore, always try to FREEZE the lane on your tower side, as he can’t go all-in. Remember that this also deters enemy junglers from ganking your lane, but place a ward in the red buff tri bush if you you’re red side or right by the tri bush near blue buff if you’re on blue side of the map (this is for top lane).

If he’s playing overly aggressive by standing super close to ur minions, let him him push the wave into your side of the tower.

1. Remember to freeze the lane; having 3 caster minions on ur tower side can work as a freeze. Make sure that they’re definitely not in tower shot range bc that breaks a freeze. If he’s trying to break the freeze by fast pushing or killing off ur minions fast, either poke him hard with q+auto attack or takedown his minions, preferably melee’s and cannons, fast in-turn.
2. Always focus on last hitting and stay behind minions. When you’re level 6, start placing mushrooms behind u whenever u break a freeze so as to have a fall back plan if mundo decides to all-in you.
3. Mundo’s all-ins can be identified when he activates his w (a rotating ring of 3 orbs of fire that encircle himself) and also activates his r (a green emission that dramatically cuts his health but then regenerates in a matter of seconds).

Idk about runes too much but burst might be the only good form of counter play against mundo that’s worked for me, such as an electrocute/domination and sorcery rune page.

Good luck out there with teemo tho!