At what troop level is GOWIPE an effective attack option?

As per TH8 you need minimum of lvl5 Wiz, lvl2 Pekka, lvl1 Golem lvl5 WB.

For Golem if you don't have lvl2 means that's okay. For pekka lvl2 is okay and lvl 3 is good. Wiz should be 5 for effective attack.

The Army combo is

1. 2 Golem
2. 2 Pekka
3. 7 Wallbreakers
4. 19 Wizards
5. lvl4 or lvl5 Pekka from Clan Castle + Poison spell
6. 2 healing + 1 rage spell + 1 Poison spell

As said above don't deploy your whole army at once. And hold few wizards for using it in critical conditions when they need or wiping corner building. Because group of wiz will die in single giant bomb.