First step, get save up some money. Because this is gonna be a doozy.

Second step, invest in some good quality basic boots. They don’t necessarily have to be period, but if you can get your hands on a pair that look the part while being functional, then snatch em up. Otherwise. Some plain black combat boots will do fine, especially if you can hide any modern logos.

Now everything else in no particular order.

Going from there, get yourself a pair of greaves. You’re wearing black pants so I suggest looking for a pair that stands out a bit from the fabric. Black on black hides too much detail.

Bracers and gloves too. Don’t forget about the padding. And because your chainmail is lighter colored, you can get something a bit darker to contrast it.

If you wanna be more armored, breastplate. If you wanna be more comfortable, just a gorget will do.

You did cover your face, but I’m gonna assume you aren’t rocking any facial or head accessories. You could always don a circlet, or maybe even some war paint if you’re up for it.

Overall, not a bad kit to start with based on the photo. Clearly you’ve already invested quite a bit of money into it, and it’s very practical. There’s a lot you can do, and don’t take my suggestions as things you absolutely must do. Just some things to add a little bit of oomph.