For a Maurten 320 I mix that up as follows (80gram serve):
Maltodextrin = 44g
Fructose = 36g
Table salt = 630mg
Sodium alginate = 500mg
Pectin = 500mg
Water = 500mL
This is a very strong mix and is what Maurten recommend however you could spread it across 2 500mL bottles (half strength) and I often do. I consume a 500mL bottle every hour.
You only really need the maltodextrin, fructose and salt. I had the pectin and sodium alginate in the cupboard anyway so use them in my home brew with no problem.