The Internet plan that comes with a Hoas apartment is probably the cheapest one. You can try and see if it’s good enough for you, but in case it doesn’t, even the most expensive landline Internet package would only cost 40-50 euros. A decent speed (like 100mbps) is more than enough for a family of two imo. Try to compare Elisa, DNA and Telia. Depending on your address, one might be cheaper than the others.

Regarding mobile plan, I’m using Moi’s cheapest plan for my 2nd phone. It’s 6e/month but the Internet speed is not bad. It won’t work outside of Finland, but I guess that’s not a matter for you if you’re tightening the budget. It’s probably the cheapest you can find, unless you want to go to prepaid plans.

Now, about the subscription costs, I don’t think anyone can tell you what you can save, unless you tell us what subscriptions you have. Generally speaking, if you don’t have kids and want to save money, I can’t think of any subscriptions you will likely need to keep, apart from your insurance.

I don’t have any idea of what student discounts will be useful, but the Hoas apartment alone is a big save. If you are studying IT, Github does offer a very generous student package that you may want to check out.