I've always used Communism but is there something else that could be more productive?

H maybe?

Theocracy! Theocracy
-20% Private Market Military Costs, don't slow me much, I buy most of my military
+40% Construction Speed, I like this part the most
-35% Maximum Technology. Still build the labs, how you want play this part of the country is up to you
+50% Maximum Population this part makes the country grow faster
Double GDI Expenses sucks, but I make so much cash I don't even notice it, Build it right and make millions each turn. and buy your bushels instead of building farms. note ye can't buy spies, and tanks, at time can be scares on the open markets. So build them , Warning ! Not having enough tanks in your country's military, can bite you in ass.

This is about as poor advise as can be made up.

First off, if anything, the +50% max population makes growing more cumbersome in the early phases of the game. It does however make theo casher viable and make theo techer stay in the green longer.

Secondly you don't need tanks if you are all-explore or if you are in a server that protects you from ABs. You should have some spies, yes. But if and only if you need tanks you buy them. This is viable sometimes even as a commie indy depending on the prices as ICs produce so damned few tanks. Theos definatly buy all tanks with their fantastic private market.

The construction speed is and always has been the key selling point of theo, but the -20% private market costs are a close second as it allows a very powerful jump in the end and if the public market is bought out, thin or expensive you always have a nice private market to rely on.

Communism. Go go indy powah