What helps increase my arena score

You need to use high BST (meaning they have a lot of stat points at max level) heroes or high merge heroes or a combination of both. Lastly, do not forget to include a bonus unit, as seen from the arena board. They change every season and some of them like the Askr trio are always there so it might be good to invest in some of those common heroes.

Using expensive skills like Aether also help with scoring. Refer to the skills list to see which ones have high SP cost and see if you can run any of them in any of the heroes you use.

Also the thing about BST is they're grouped in BINs of 5. A hero with 145 BST scores the same as one who has 146, 147, 148, and 149 for example.

Hi there!
There are 4 main ways to increase Arena score.
1. Use higher BST units. This is normally armored & dragon units, which is why their so common in higher tiers.
2. Use skills that require lots of SP. Most of these skills are good too, like DC and Wrath. If you have them, it might be worth it to sacrifice the unit for the better unit & score.
3. Merges. Merges increase BST, so they also increase score. However, many great units can only be found at 5*, so it's hard for a FTP to get 10 merges.
4. Blessings. These are new, but if you bring in the right blessing and legendary hero, blessings will also increase your score.
Hope this helps!

Like and fjorm are good solid units that will boost your score to 700 thanks to their high cost skills. They make a good duo too.

Good units that synergize with those two while keeping score high are
Bk, bike, myrh, green dc units/fliers

Use expensive skills like aether, drive skills
Merging units