I'm a foreigner student who will do a master's degree in germany but as you know I need a health insurance plan. I looked up a little and found out that there are various options. One of them is AOK but it's 83 euros fee (aprox) which seems too much for me so I'd like to know in your experience which are the best economic options for students.
Bar some exceptions (that likely do not apply and that I would not advise you to make use of even if they did) you have to sign up for a "gesetzliche Krankenversicherung" (statutory health insurance as opposed to private).
The monthly fee (and service) varies very little between the different insurers and you will need to accept that cost as part of your studies. In exchange you get good health care that is fairly cheap (you are effectively receiving subsidies from the other participants in the insurance scheme that pay a percentage of their salary instead, typically much more than 83 EUR a month).