Choosing the right faction will allow you to develop your character in the way that you want. Each faction has characteristic features and abilities that are suitable for a specific play style. Because of that you should really think hard about selecting your faction.
If you want to use spells, Berserkers are a perfect choice – in the world of Elex, Berserkers are the ones that perfected magic. Their abilities allow them to summon ghosts, quickly heal their wounds or increase their damage. They can enchant weapons (but only those that come from old times – axes, swords, hammers) and send a few arrows from a bow at the same time. Berserkers allow you to create a character that uses melee attacks and supports himself with spells and a bow.
Outlaws' skills allow you to create a character that uses rifles (those which shoot regular bullets, not plasma). They also spend a lot of time on using workbenches. Outlaws offer a lot of abilities that are useful during crafting – thanks to that you can create weapons, ammo and stimulants that grant you various bonuses. Besides that, you also get access to dismantling weapons which allows you to get parts that can you can sell or use in crafting.
Clerics are a perfect choice if you plan on using ranged weapons a lot (especially various energy and plasma rifles) and support yourself with abilities that resembles magic. Clerics have access to PSI abilities that are similar to spells – they allow you to use power waves, teleport at a short distance or create holograms.