Depending on what you want, & what era, class or geographical region ("medieval" spans 500-600 years), prices tend to start at $80 for an unadorned breastcollar or crupper, $200 for a simple bridle
to $4000 for a full-out pre-made actual metal armour.
For tack, you see used Spanish or Portugese presentation sets. Just run a search and you'll find a handful of sites. Or search the brands/makers Zaldi or Ludomar. Or see the thread here started by CacheDawnTaxes
. But again, I've never seen "cheap". I've seen somewhat cheap from Spanish or Dutch dealers, but you wind up paying a lot in overseas shipping.
Most barding, trapping, or breaching is custom made to your horse, so it's pretty hard to find already constructed costumes. Here's a site that produces custom costumes, and has some useful information: Cercle de la Croix
. By the Sword
is the only place I've seen museum quality replica of full armour (you can also get just Chamfron replicas in different styles) but the are mucho pricey!!
To do yourself, I've seen numerous patterns, though I don't know links off the top of my head. The FHANA recently published an article w/patterns but I no longer have that issue. Sorry. The full-out blankets are probablly easiest to make but they're mostly used for show, in jousts, to use colour and heraldry to show status/ownership, as a horse will over-heat in it as riding or "battle gear". The ultimate in homemade ease would be rein and body Caparisons. You can find premade designs at Franga Designs
, along with other articles and fun stuff like horn/floral wreath/plume browbands, saddle pads et cetera...though they have a more child- or doll- like, or "carousel", feel. Still nifty (and inexpensive!), though! Great for kids!
Some of the simpliest ways is to dress up your own bridle with rein swags, or covers, and use an ornate, but not overdone, saddlepad. The nicest I've seen are made by Medieval Horse
, though they are a bit pricey. Or there's some available at Dark Horse Farm Designs
You can also dress up your browband with a posh addition from Equus Couture
or Bella Equine Design
for more of a fantasy, romantic or mythical look. And then spend a bit more on your own outfit.
When you get your outfit together I'd love to see pictures!!