Hello! I'm not new to skincare but I'd like to get some recommendations from people regarding which exfoliant to incorporate into my routine!

My current routine (both AM and PM) goes like this:

1. Cleanse - Round Lab 1025 Dokdo Cleanser
2. Tone - Dear Klairs Unscented Supple Preparation Facial Toner
3. Serum - The Ordinary Niacinamide 10% Zinc 1%
4. Moisturize - Illiyoon Ceramide Ato Concentrate Cream (New)
5. Sunblock - A'pieu Madecassoside Sun Cream (only when I have to go out, which happens about twice a month) / A'pieu Pure Block Daily Sun Cream (still haven't started using this, but it might be my go-to once I start using retinoids because it's cheaper)

I have oily Fitzpatrick type 4 skin. I used to think I had sensitive, acne-prone skin too, but I figured that was probably because I destroyed my skin barrier (the culprits being the CosRX Good Morning Gel Cleanser and Skinfood's Black Sugar Mask).

My skin is highly-prone to post-inflammatory hyperpigmentation so I still have a lot of acne marks from my breakouts before I started using niacinamide. I already bought the TO 2% Granactive Retinoid Emulsion to help with the fading (haven't started using it yet because I'm still waiting to see if my skin reacts well to my new moisturizer), but I thought I should be exfoliating too.

Since I've committed myself to being more gentle with my skin, I'm looking to replace my old physical exfoliant (the black sugar mask) with a (relatively) gentler chemical exfoliant.

Does anyone have any cheap recommendations (ideally less than $20)? I thought about getting either the CosRX BHA Power Liquid or the TO AHA 30% BHA 2% Peeling solution for once a week exfoliation, but I want to hear what other people have to say before committing.

Thank you!