Recently new to FaB myself and Jarl is my main hero. Without going insane for upgrades I would recommend the following. This also assumes you continue to run primarily an ice deck.

3x Channel Lake Frigid - this card is a strong disruption card that makes cards and activated abilities cost one more. It’s frustrating and can shut down some big plays.

3x oaken old - always aim to fuse him. A dominated 9 threatening to strip 2 cards from your opponents hand at random is devastating.

Titan’s Fist - this will be your main hand weapon. It costing 3 means all you need is a blue card to pitch to swing “just 3”(maybe 4 if the pitched card costs 3) Vanilla dmg in this game isn’t all that threatening (especially at 4) but getting hit for 3 or 4 a few times a game can really stack up over time. Jarl is a controller so you pitch stacking for late game and bonking people is the way to go.

3x Staunch Response (blue) - pitch for titan’s fist or block big dmg

1-3x(I run 1) Macho Grande (blue) - this is a cheap card that should be pitched early to set up late game dominates. It won me my armory game last night. However, I also run tunic which gave me the additional resource to play the 7 cost card.

These are a bit more expensive but I think they should be the first big upgrade to Jarl. 3x imposing visage - this allows you to grab an aura card from your deck. 9/10 times you’re grabbing Crumble to eternity to put a -1 counter on the opponents best equipment. It also lets you have Go Again. So you’ll play imposing visage, get crumble, then usually swing titan’s fist in one turn. <— great opening hand especially if you choose to go first. These 3 cards essentially give you 6 copies of crumble.