It obviously needs some control elements, etc, but the engine is really starting to take shape.

Man you're fast on the draw. Give // Take + Chasm Skulker at all viable or am I talking nonsense?

I've used these both before, with Lorescale Coatl tossed in the mix, and thought of them as well. They could work. But that would definitely be slower and possibly need a strong control shell. You'd need to draw 10 cards and Take the counters to hit 20, or put scales out and draw 5. In order for this to not be 8th+ turn, you need a decent amount of draw. That leaves only a little room for the control elements we need, and we're starting to count heavily on our deck to draw decently and get our "combo" out. I couldn't get any kind of shell that looked like it would work for me, but someone might find a better way.

If I went with Skulker, I'd drop Rishkar and look at both Give // Take and Bioshift. It's important to remember that "moving" counters is actually removing and adding, so it triggers. This is also how Scrounging Bandar becomes a decent card. Perhaps Quirion Dryad and/or Deeproot Champion would fit in there as well, since Give/Take and Bioshift both want us to focus on growing a single creature big. Focusing the counters on specific creatures also means that a well timed removal spell hits us hard, though. Again, that feels like it would want to be more of a control-combo than an aggro-combo.

I'm not sure Skulker and friends fits well within this deck. I feel like Nissa and Thrumingbird are both integral cards that compliment each other and run the current core. Moving away from them would be a different deck, really.

A bird and two critters means that if you drop Nissa & -2, you add three to Ascendancy, then proliferate for another four. That's seven counters in one go - thirteen if you have Scales out. The critters that you run aren't as important with those in place, but you do need them to have their own counter method for when Nissa isn't showing up. Servant of the Scale and Simic Initiate might have better replacements, but they function decently.

Honestly, for what I'm looking at, I want some kind of cheap way to quickly move counters back and forth. It would take it to the next level of getting there quickly. Simic Guildmage's ability is right on target, but it's too mana intensive to get us there.

It's close, but i want to make some cuts for more room, while still upping the growth slightly.

I always run 2x Cytoplast Root-kin in builds like these. They are awesome with Hardened Scales.

What would you do with this if allowing a larger budget?

I haven't tested any real non-budget cards, but one idea looked exceptional.
It's a completely different deck, but worth noting how no-budget can open better options entirely.

Arcbound Ravager immediately sprung to mind when I saw Ascendancy. Although that would require a completely different shell, I can't imagine not finding one that works well. Ravager's counter creation gets insane fast. If you have scales out, it would realistically only take 4 artifact sacs to pop ascendancy. Those four add eight counters (+8) to Ravager, and then sacrificing Ravager to himself modulars his 9 counters (+10) over to another creature. That's +18 counters on ascendancy, so if you did any other thing before now, it pops.

His awesome sidekick is, of course, Steel Overseer. Again, we're getting a lot of bang for our buck. You're adding your creature count directly to Ascendance every turn, and scales/etc makes it ridiculous.

Hardened Scales Affinity is something that already sees some minor play, and I think Ascendancy is the thing that'd make it a real, seperate deck. Ascendancy would push it further away from "Affinity" and closer to "GU Modular Scales" or something.

Arcbound Worker, Chronomaton, Hangarback Walker, and Walking Ballista are all contenders worth testing. Metallic Mimic naming Construct becomes a possibility.

The important thing to note here is that you're going to end up with a fast paced, hard hitting aggro deck that has an alternative wincon. It would be a bit less aggressive than Affinity, but it would gain a strong, surprisingly fast way to win against Ensnaring Bridge and other stop gaps.

I'm sure there's several ways to build Ascendancy, but this seems like one of the strongest ways to make it pop when budget isn't of concern.

Edit:
Animation Module would be worth playtesting, and was worth this edited-in paragraph. Module + Overseer is an engine in itself, creating an ever-growing army of ever-growing critters, limited only by your mana. If Ascendancy, Overseer, and Module are the only cards you ever play, and you top out at 4 mana, you hit 20 counters on Ascendancy by turn 7. Thats alone isn't awesome, but you've literally only played 3 cards and end up having a critter army totaling over 40 power.

Module also synergizes directly with Ravager. Sac an artifact for a counter, pay 1 to make a new critter, rinse repeat. Again, you're growing Ravager and counters limited only by the mana you have out. This isn't aggressive enough for Affinity, but looks like it'd fit into this divergent path.

Edit 2:
I thought it through enough that I created the basis of what I'd look at building Here

Obviously the first non-budget addition would be Misty Rainforest, but that's a cop-out answer

I think that if you're going non-budget, the cards that you look at are Doubling Season (probably too expensive at 5, but has to be considered in any counter deck), and Noble Hierarch to get things moving faster and to help our fragile Thrummingbirds.

I could see this going in a Deranged Outcast direction.

Hm, maybe in a format where you have access to Reyhan, Last of the Abzan. Sultai-colors mana shouldn't be hard to do, and you can have a nice solid Human theme and do silly crap with Village Cannibals

Would it be worthwhile to swap Servant of the Scale out for Iron Apprentice?