Help create my setup!

Hi everyone. I thought I was doing ok with laundry until having kids and after coming here it's like I'm a total begginner again! And since I'm in another country (Spain if it helps), this adds a layer of diffculty in selecting products for my setup, so I would like your help.

• So far I have done away with clothing softener but I haven't found citric acid rinse anywhere. Can I use the powder from the hardware store? What about vinegar? I find it odd but I'm willing to try anything
• I have found sodium percarborate in a bag and it changed our lives but maybe I'm not using it to it's fullest potential. So far I put one scoop (30g) per load and I do a soaking tub with 30g and hot water to soak kid's food stains.
• Vanish oxy action powder exists here but it is prohibitely expensive. How can I check if other brands are good enough? what am I looking for?
• What about a detergent? I have a basic store brand powder with the soap bar in the front, but what should I be looking for?

Most brands and products mentioned here simply do not exist in my area, can you point me in the right direction? I'll be happy to contribute to a general worldwide guide with my findings :)