To get a local phone number, there are 3 mobile operators (Bite, Tele2, LMT) offering monthly plans or prepaid cards. You can find them in official stores or in bigger grocery stores (Rimi and Maxima) at the cashier desk.
The public transportation provider in Riga is Rigas Satiksme (https://www.rigassatiksme.lv/en/). Public transport system in Riga is relatively convenient. There are buses, trolleybuses, trams, and minibuses. All of the transports mostly follow the schedule, except the rush hour as worldwide.
We suggest using an electronic card (e-talon), otherwise, it will cost you a fortune. You can get it in customer service centers.
Also suggest downloading offical app Riga Card to see schedule on your phone. Yet Google Maps also provide the functionality.
Bolt and Yandex Taxi are most preffered as they have own apps. Otherwise also reliable Baltic Taxi (call +371 8500) and RedCab Taxi( +371 8383)
Electric scooters (Fiqsy/Atom/Bolt/City Bee) and bikes are possibly the most convenient transportation in Riga, especially in summer and spring/autumn. Though, you have to be very careful when you leave a bike unlocked in the street, as there are quite frequent thefts. Lock your bike properly.
RIGA STUDENT MARKET in facebook can be a good option to buy a bike or other useful stuff for your studies.