What level should my walls be before th 10?

I had all Legos and 30 lavas when i upgraded.

At the moment my TH is upgrading to 10. I have all level 8 walls and a few in the center that are level 9. I really think that you only need to get your walls to level 7 before upgrading as a MINIMUM. I am trying to get about 50% of my walls to level 9 before my TH finished upgrading though, just for cosmetic reasons.

9 minimum maybe a few 10

I would say full Legos minimum. Anything else and your behind before you even start TH10. The more lava walls though the better.