I have tried out many so called chess variations (sometimes chess related games) in my life. Not long ago, I was introduced to the Economy Chess (EC) and I think I`m gonna like it even more than Stealth Chess played in the Ankh-Morpork Assassin`s Guild. 
Basic Idea
If you want to know all the rules please go to the Economy Chess group. EC is played like standard chess but you gain coins during the game that can be used to buy and place a new piece/pieces on the board. Each player "owns" squares where their piece was the last one to be on. Every player owns 16 squares and has no coins before the first move. Let us make a couple of moves:
Black owns 18 squares (7th and 8th rank + d5 + f6) and White 17 now (1st and 2nd rank + g3). At the end of each player`s move a calculation is made: number of coins owned before the move + number of squares owned after the move - number of his/her pieces on the board after the move - number of coins used to make a move = number of coins owned after the move. (There is an option to use a rule that a player receives the opponent`s coins by promoting his/her pawn.) It means that White has got 2 coins now and Black 3. These coins may be used to buy new pieces under certain conditions (see rules for details).
Buy one get 23 free
It isn`t right to say buy when it comes to EC for the software you need is free. Before you start your game you have to agree with your opponent on rules you will use. Since there are 3 categories with 2 options and 1 with 3 options you can play 24 more or less different games. Another thing is that you are free to determine how many pieces of each kind you will be able to buy during the game and how many coins you`ll have to pay for each kind, e.g. default settings are - 8 pawns, 25 coins each. Unfortunately, it isn`t possible to set the number of available pieces and their cost for each player which would make this game (these games in fact) even more flexible for a weaker player could get a bonus, i.e. cheaper pieces or more pieces of a kind. Nonetheless the latter may be just agreed, e.g. I agreed not to buy rooks and queens when I played my wife.
Although I am going to try all the combinations this post is written about games played under these rules:
- placement - on original spot
- production - may always produce
- promotion - steal cash
- movement - produce or move
- default quantity and price of available pieces, i.e. pawn 8/25; knight 4/75; bishop 4/83; rook 4/113; queen 2/219
Opening stage
Opening stage may be defined as the beginning part of the game when players haven`t got coins enough to buy new pieces. Under the above conditions (prices) it would be about first 14 moves. A player has to play the way it is common in standard chess (to develop pieces ...) but they may not forget about their coins. I like the Czech Benoni but although the below line is not bad and it is playable for Black it may be a problem in EC.
White has got 54 coins (current income 8 coins/turn) and Black has got only 36 coins (5 coins/turn). I was kinda lucky when I played my first game for although I didn`t care about my coins much I achieved a better position without lack of coins.
I had 71 coins (10 per turn) and my opponent (Black) had 73 coins (10 per turn).
Middlegame and endgame
The game becomes very interesting, demanding and funny when players have got money enough to buy pieces. A move that would be a blunder in standard chess can be the best one in EC. A won position may become a lost one in one move. Just an example from my games played with a friend.
But Black had coins enough to play $Ra8 (i.e. to buy a rook and place it on a8).
Consequently, if players think of their move they have to take into account how many coins their opponent`s got and what pieces and where they can place them. It makes the game a real challenge even when you play someone you would beat in standard chess. I played a single game with an option "placement - anywhere on backrank" and it was pretty hard for new pieces don`t have to be placed on squares where they are in the beginning. Plus do not forget a player can buy more than 1 piece at the same time.
Endgames involving pawn promotion are tricky in EC if "steal cash" (or "steal cash and promote") option is used. The below position is a win for Black in standard chess but it doesn`t have to be like that in EC - it all depends on how many coins players have.
Black will promote their pawn after White which means White wins in standard chess. But in EC, White will get all the Black`s coins when they queen their pawn (the pawn will be removed if "steal cash") but Black will get all the White`s coins when they promote their pawn. It means that White will be left with no coins and King only and Black will have plenty of coins to buy pieces and their King. But the game would likely be different if "steal cash and promote" would be applied for White would have no coins but King + Queen and Black would have all the coins but King only. I think noone would promote their pawn and they would just buy new pieces.
Chess engines
AI should be added when a new version of the software is released. Chess engines can`t be used to play EC for obvious reasons
- they know nothing of owned squares and coins,
- they wouldn`t expect an opponent to change a position dramatically by placing one or more pieces,
- they wouldn`t suggest to buy and place a piece,
- those I know can analyze legal positions only, which means that they won`t work if a player has more than 16 pieces.
Give it a try
I am sure the game is worth trying. I hope to post some analyzed games and hints how to play soon.