Wow, this achievement takes so much time to complete.
You can collect Terra tokens in three ways as of v0.8.008 update.
1. Collecting from random crates on the ground. Opening each crate has a chance to have stack of tokens. Each stack is around 100-1000 tokens. Searching existing crashed ships is an excellent way to accumulate a few thousand.
2. Fallen ship crate. Randomly ship will drop from the sky with 4-5 crates. Crates can have stacks of 100, 1000, and 5000 tokens.
3. Space Trading Rockets. You will receive mail with the recipe after achieving the breathable stage.
The maximum amount of tokens from a rocket is 250 tokens.
Each rocket takes about 10 minutes to make a round trip.
Build as many Space Trading Rockets as possible and automate building and sending pulsar quartz/circuit boards to optimize how many tickets you get.
***Edit***
As of update 1.0, the quickest active way to farm terra tokens is to use the Portal Generator to loot "Production & Energy Multiplier Fuses" from distant wrecks.
Production multiplier fuses are worth 5000tt each and energy multiplier fuses are worth 6000tt each.
The quickest passive way is having auto crafter create Pulsar Quartz or Fusion Energy Cells. Energy cells are 80tt each but take more materials to make.