Everything
IMO the bare minimum you would need before going to TH11 is a good army. Maybe a good farming army (barch or miners come to mind), and good war army if you do wars. Heroes should be at least level 20, though 30s or better will be great to start TH11
Defense-wise, just try to make sure you aren't too rushed. It's okay to leave lesser defenses (e.g. cannons, archer towers) at TH9 standard if grinding to build them up would detract more from your experience than going to TH11 and playing with the stuff there. If you're more active and can loot more than you lose, feel free to leave them a little rushed when going up. Otherwise it might be worth it to upgrade defenses as much as possible.
Ideally two defenses you might want to max in both cases include air defenses and inferno towers (you can think about holding off on doing the latter if you're serious about war, since upgrading them could drastically increase the difficulty of the opponents you face). Good air defenses are vital for defending against edrags (TH11s often won't mind dipping to hit TH10s from time to time) and laloon among others, while infernos are versatile and can be used to curb farming attacks with multi mode or deter sieges/queen walks with single mode.
Lab: As stated above, the minimum should be upgrading one farming army and one war army. But upgrading more units in the lab will open up more options for use in attacking, especially in war.
Your lab upgrades if possible max it all. You can then choose what troops to attack at th11 much easier. Heroes min level is lv30 for both BK and AQ. Upgrades ur wiz tower, inferno tower, air defense maybe archer tower and xbow as well. And unlock all troops and spell available. The rest you can upgrade after that. Those above are far more important bc th11 you need a good attacking army. Defense IMO semi -maxed to max is ok. Im now maxing my defenses to max th11 i max my th10 defenses at early th11 stage. Just upgrade the essentials.
Ok, Thanks for the help, i would upgrade to Town Hall 11 once i have 35 king and level 12 cannons and archer towers.
What do you think?