giveaways!!!

What 1:1? You want to trade a game or you want to give away a game?

If 1:1 you mean only for one person then you just make a Invite Only giveaway and give the link only to that person. Note however that this will not earn you any CV, for the giveaway to give you credit it needs a minimum of 5 entries.

If 1:1 though you mean you give them one and they give you one then it's not a giveaway, it's a trade so proceed to SteamTrades :P

Use these custom rules:

ratio_real>=1 for Ratio for real CV sent/won.
ratio_raw>=1 for Ratio for steamgifts CV sent/won.
ratio_number_giveaways>=1 for ratio for number of sent/won giveaways.

do you mean 1:1 ratio of giveaways?

You don't need any special customization. Just go to Manage Giveaways on that site, put in the link to your invite-only giveaway, and then adjust any of the following parameters at the top:

Ratio for Real Sent/Won CV <-- Checks actual CV ratio
Minimum Ratio for number of Sent/Won Giveaways <-- Checks quantity of games sent and received
Minimum Ratio for RAW Sent/Won (Bundle full CV) <-- Checks the ratio listed on the site, that gives full value for bundled games

Set the Minimum or Value column for any of those you want to use to 1.0, and you're set.