How do i increase my Economy

I started playing this game 2 years ago, and played a lot for a year.

Recently i came back after a stop for a year. Modules are a totally new thing for me.

I struggle a lot with progression. Im constantly farming for coins to up my Health or Damage. I average around 300M-400M coins per run. I mostly run on T4 because i can get my Death Wave Max health on there. With luck on the perks i can go up to 600M-700M coins.

I just dont understand how people earn Billions of coins. 1 run of mine takes multiple hours and i can mostly just complete 1 run a day.

Is there something im missing thats costing me loads of coins ? Or am i doing something wrong here ?