How to adjust UI and game board for different android screen sizes?

Before anything else I've already searched about this before posting this question. This is more of a confirmation of what I've understood by what I've already read.

About my game...I'm going to create a simple 2D Board Game.

It's a 2 player turn-based game. Each player will have 3 "coins" on their side.

[x] [x] [x]

[ ] [ ] [ ]

[o] [o] [o]

Each player will then have 1 move per turn. They can move their coin diagonally,vertically and horizontally, given that they have a space to move to.

The goal is to have a Straight/Diagonal line of coins for you to win the game like this:

[x] [ ] [ ]

[o] [x] [ ]

[o] [o] [x]

You cannot win if you form a straight line on your own side, you can win that way if you are on the other side of the board(opponent's starting position).

I don't know if I've explained it very well but that's the summary(I guess) of my game.

Now about the adjustment of UI for different android screen sizes... Here's my UI design:

From my understanding I could use an ortographic camera and use it's methods or I could use the methods of the Screen class to get the resolution/size of the device's screen size and then do some calculations to adjust my UI(buttons,text etc).

How about my board? How will I be able to adjust it to different android screen sizes? My target devices would be 7 inch tablets and some android phones that has around 3"+ screen size.

Should I just do a small scale version first and then just build it again using a bigger screen resolution?

Oh and by the way this is only for a school project. Anyway I would appreciate some insights about my dillema. I haven't quite grasp the concept of screen resolutions and aspect ratios yet,I mean not that extensively.