The important thing to remember, when it comes to Mandalorians and making a Mando character, in my opinion.
1. It's not a race but a culture, a way of life.
2. Any sentient species can become a Mandalorian.
3. Depending on what type of era Mandalorian you build your character from, you have your classic conqueror Mando, your Bounty Hunter Mando, your Warrior Mando and etc.
4. Armour is a Mando's soul, especially for the current era Mandos you see in canon and is one element many many Mando writers spent time on creating their own unique armour (though it's not needed if you just want a classic Mando look and do Mando RP).
However, the most important thing you can do is write the Mando you wanna RP, whether that's inspired by Boba Fett, Jango Fett, The Mandalorian or some other cool character you read about or saw. It's is up to you.
There is no wrong type of Mandalorian.