Each day you will be given 6 Technos for completing your job (which consists of a task for Rad, Enid or Mr Gar) after you punch out. There is no need to rush buying cards or boosters so feel free to save this pay up for the trophy or you can also get it later once you've unlocked the ability to sell Microchips and card duplicates to Dendy.
This requires you to have 50 on you at once to unlock - not just earn 50 - so hold onto the money you make and it will add up fast.
The game continues once you beat the story so don't stress - you can easily complete this later if you focus on completing quests and buying cards & boosters.