Not particularly much actually. Your first point of order might as well be getting yourself some clothes and the simple hose and T-tunics aren't that difficult to make.
Linen shirt
Linen brais
Wool tunic
Wool hose
Once you have those, you get turnshoes, again, not that expensive.
And now you're actually set for a good kit to be either an 11th or 12th or 13th century knight. The cost comes in upgrading your armour, and that's where the 13th will be more expensive than the 11th (11th requires a conical helmet and you're done, whereas 13th will require a gambeson, greathelm, maille hose and longer sleeves).
My advice would be to look through what people wear and find the period you want to do proper, and once you have that down, you start building from the inside out. I.e.
Undergarments
Civilian clothes and/or Arming Clothes if they existed (no gambesons in the 11th century really)
And then you start layering your armour on top of that. And you're not that far off from the 11th already, and you would still be doing a very ok 13th even by just slapping a greathelm with your Torse and mantle on top of what you have =) (Although, again, boots and bracers should probably go). Ian L did an amazing job at "So you want to buy some armour" at the top of the posts.
Here's a funny thing though.
You can actually do another period.
And your Maille is great for it.
14th century.
You add a 14th century greathelm (or, honestly, ANY 14th century helmet you like).
You add elbowcops with your leather bracers.
You make yourself a pair of leather greaves.
Get kneecops.
And sew yourself a pair of padded cuises.
Now you're wearing tournament gear from the 14th century. To this, you can later add a coat of plates, or a lombard breastplate. You can, if you want to, add one of those huge crests on top of your helm (if you get a greathelm) and have it nested in your Torse and mantle.
But again, for this transition, you're also going to need:
Shirt and braies
Hose (might I suggest one yellow, one black if those are your colours? Or both yellow if you make your cuises and greaves black)
A thinner aketon or pourpoint to wear beneath the maille and to attach your new, spangly elbow cops to.
You could very quickly become very iconic, and, when you have more money, or time, you can, as said, start upgrading your kit into any 14th century direction you want to take it. Be it plate, splint, early, mid or late.
EDIT:
Here's a fine Danish gent in, what is assumed to be, leather greaves
https://www.flickr.com/photos/roelipilami/1623517375/in/set-72157602468647900/There are also plenty of pictures from both Germany and Italy of maille being worn down to the elbow, with a cop and then a bracer. It is the leather bracers as standalone defenses that is of hollywood make, but, with an elbow-cop and maille and possibly even more protection under the maille, it is fine. And, as said, with laced up leather greaves and bracers, elbow protection, knee protection and gamboised cuises, you'll have a fine tournament gear.
