It takes quite a while to finish the main story in Wolcen and to get a character up to a high level. Don't worry, though — things should go more quickly with your second or third character.
The reason for this is simple — the Champion of Stormfall mode, unlocked by completing the campaign, is available for all the characters in your account in the corresponding game mode (online or offline).
This means that you can completely ignore the campaign with your new character if you wish, and quickly begin the same activities as with a high-level character such as mandates, then expeditions after a few levels. This is much more intense, and profitable in every way.
It doesn't stop there: you also get all the bonuses already unlocked in Stormfall, such as changes in the merchant's prices, the fifth skill, and potentially much more depending on what you've achieved with your other character.
You can also continue to rebuild the town and send researchers and diplomats on missions to bring you gold and primordial affinities.
You can also use all of this primordial affinity to quickly level up your skills. Your character will have no trouble quickly leveling up if he's fighting Level 40 or 60 monsters. Having a high-level mobility skill also helps to speed things up a lot.
You can also launch the campaign after filling up with primordial affinity, or even levels, in Champion of Stormfall mode. It's an easy way to complete many Steam achievements, such as finishing acts without dying.
Potions & Gems
Potions have no level limit, so you can use this feature unlocked by your first character to heal yourself of 20,000 health and/or recover a lot of willpower/rage.
Gems don't have a level limit either, so you can use the best ones in the game, especially on your weapons. Bonus weapon damage or spell damage makes a huge difference.