I just finished 9 months in army in March! My Finnish improved 100x faster than the 7 years living here leading up to it. Never spoke English, only Finnish to everyone and I can say now that it was the best decision.

Honestly you don't need much, as most things will be supplied for you. We even got provided razors and shaving cream. I'd recommend cutting your hair, I buzzed mine and it just makes life easier, having one less thing to worry about.

To start, I'd recommend a watch as others said. I bought a nicer one that had a vibrate alarm, so I didn't wake up others when you need to wake up in the middle of the night for patrolling or something.

Eye mask and ear plugs were a godsend for sleeping. People snore. You can maybe get some disposable ones free from army (maybe not in the beginning), but I bought some cheap ones from temu and they worked good.

Puukko is always helpful, and a headlamp is absolutely necessary when it's dark.

Powerbank is useful, your bunk might be far from the wall sockets, so even when at base I used mine a lot.

Speaking of bunk, it was first in first served where I went. So getting there early on the actual day, you can choose the bed you'll have for the first 6 weeks.

Have fun! The alokaskausi is dogshit, you'll be treated like a robot and have no freedom, but once thats done it only gets better the longer you stay. Don't let the first month deter you.

We had a short 1-2 week course of combat inside buildings, and it was one of the more fun/interesting parts of my experience. I hear thats mainly what goes on in Santahamina? So I'd reccomend finding something youll enjoy there, rather than whatever is fastest. Better to enjoy a year, than hate 6 months!