Low cost to start for your requirement:
1. Change crankshaft pulley to lightweight type
2. Use aftermarket performance air filter
3. Use spring buffer to reduce excess rebound movement

As for my car:
1. Arospeed, but Honda got lot good aftermarket brand (Spoon, Works Engineering, etc,...)
2. Simota / HKS / K&N
3. AMT is cheaper, but if can afford Orsen is good. Little bit expensive..

Total all less than RM1k.

I bought online & installed by myself.

For now I'd prefer upgrade intake side first (air / spark plug / fuel). Then exhaust side (manifold / piping / muffler). But also up to your personal preferences.

Intake side upgrade that I mean is from performance air filter (OEM shape or change to open pod type) to throttle body (add-on any device or use widen size) to performance spark plug. But remind you that all upgrade will cost you bit higher FC than original standard config.

Just talk to my mechanic, his first basic recommended method is to add throttle controller like Works Engineering e-Drive 3.

Your gearbox already show failing symptom. Try to add ATF enhancement like JV Lube or Nano Estremo first & see if can recover.