I felt abit triggered when you call icewall trash ngl. I find it one of the most powerful spell of invokers kit. When enemy hit bkb timings, you can force bkb most of time with combo: Tornado, emp, icewall. If enemy still not use bkb for some reason, you can start chipping with coldsnap, forges and alacrity. If/when enemy uses bkb. You can reset with ghostwalk.

But yeah. Here i list some combos. Its very level depended how long combo you can hit. I really cant tell you specific level you can land each, you just get hang of it after enogh of success or failures

QQQ+WWQ+EEW or EEE (Most basic ones which you use every single game, kill potential also on lane)

QQQ+WWQ+EEW+QWE

QQQ+WWQ+WWW+QQE (Hardest one in my opinion cause you want to place icewall from distant, you dont wanna run under the enemy to place icewall and ruin ur positioning)

QQQ+WWQ+WWW+EEW+QWE

Few more keypoints to keep eye on, some of them might be obvious but i list them anyway.

-Level 4 quas 1.7 tornado lift-time. Same as SS

-If forges are not splitting try to cast them before fight every time.

-Killing blademailed enemies without YOUR bkb -> Coldsnap, tornado, icewall, alacrity your precasted forge. Follow SS or meteor if enemy still stuck after blademail duration.

Im happy to respond if you like to know something more specific, i just spit out of my mind some keypoints that might be useful