Codice fiscale, money and a bank account

Codice fiscale (tax code) is free and needed for enrolment, SIM, bank and rent. Get it at an Agenzia delle Entrate office, through your university's welcome desk, or ask your embassy if it issues one before travel.
From Bangladesh: open a student file with an authorised bank to send fees and living costs legally; ask your bank for the current Bangladesh Bank rules. Keep receipts.
On arrival: some euros in cash plus an international card.
In Italy: open an account once you have the codice fiscale; some banks ask for the permit receipt too.
Keep the visa money in place. You show funds again for the permit and each renewal.

This page explains official rules in plain language. I am not an immigration adviser and I do not give visa advice. For that, always use official government sources. Rules change: confirm with your university, the embassy and VFS before you act.