Controlled Chaos

This is actually getting close to my favorite type of build in magic, the instant control synergy. You are doing something slightly different than usual here, as you're going for big spells reduced in cost, but most of the principles remain the same.

There are a few problems that need to be sorted out though. Firstly, and unfortunately, Isochron Scepter doesn't let you pay the X cost on instants and sorceries, so you can't put Electrodominance on it. As such, you don't actually have any cards you can imprint directly onto isochron, and have to rely on the cost reduction effects to 'sneak' a Chaos Warp onto an Isochron, which is both very unlikely and ultimately not a great idea, as the math on it happening is minimal (2 copies of isochron, 3 copies of Warp, + needing a reductor). So, either drop Isochron or you'll have to add some instants to imprint on it.

Secondly, even though you're going for cost reduction on larger spells, you're only running 6 cost reductors and 20 total instants/sorceries (almost all of which require lots of mana), so you're much more likely to have a hand full of cards you can't use than being able to reduce and move quickly. You've also got a lot of [I need instant/sorcery cards to work] cards that aren't instants/sorceries, which ups the potential for hands full of nothing. I'd recommend cutting out some of the supported cards and upping the instant/sorcery count while also going for lower cost instants/sorceries (2-4 drops) so you can play things sooner and still take advantage of the cost reductors when you have them.

I'd also say swap out a few islands for [[Lorien Revealed]], as this deck has no 1-drops and it synergizes perfectly, but that's a $2.00 card, so not sure if it's in the budget.

Then there are a few cards that I'd say to cut entirely:

Mana Geyser is just a bad card in general (it's so conditional) and is really only viable in commander (where you have multiple opponents and can potentially harvest 10-20 mana per use). It also is a 5-drop, so by the time you can play it, you can play most of the cards you wanted to play anyway. That's a hard cut from my perspective.

Commence the Endgame isn't worth the 6-drop cost. I know you want the token as a damage clock, but for a 6-drop, you could be laying much more effective/damaging spells.

Just some thoughts. I've never made a deck exactly like this, I always opt for the lower cost instants/sorceries and triggering off of casting them a bunch instead.