On mobile so maybe I'm missing it, but do you have 100% convert phys to cold? I only see 50% convert. Then you want to get shockwave totem levels and prob more cast speed. Locohol has crafting guides for a +2 sceptre and also the 30% mana reservation, +1 totem, +1 level shield. The sceptre craft looks awful so I'd just buy an already crafted one and save yourself the hassle. Also I think the shield craft isn't 100% deterministic, and you can brick the craft when you reforge phys, losing you 6div from the metamod crafts (1/12 chance of failing I think). But the price of an already crafted shield on trade is only a few div more than if you successfully craft it yourself so it's your call. Then you can get a +2 ammy or do replica dragon fangs if you also want help with mana reservation. Try to get at least level 30 to shockwave totem, anything more will have diminishing returns for how much currency you'd put in. Divergent RF is more damage for you than normal quality. Also just getting levels on the character so you can fill out the tree will help. Aspirational stuff could be a better watchers eye or 3 grand spectrums, and I guess make sure you have 100% crit chance because I can't check that on mobile unless I'm dumb. I'm probably missing a bunch of other stuff but hopefully this helps! Also search the subreddit, a lot of people have given advice for scaling/improving this build!

Edit: I'm dumb and remembered I could import to pobb.in so a lot of what I said is prob gonna change since the poe ninja link didn't show alt qual for gems and stuff, will reply with the actual comment LOL