0.5.5 Fubgun Flameblast Oil Grenade

Early boss kill order for a smooth experience:
Devourer(Mud barrow) > cold witch(Clearfell) > hut witch(Grelwood) > rust king(red vale)
If you're more experienced, feel free to skip devourer. Devourer gives an extra support gem around -2 minutes, it's quite valuable for players who struggle in act 1.

For campaign you're just looking for basic gear with life+resist, generally resist is more important. For rings/gloves, these are pretty good pieces to pickup flat damage to attacks, as it'll boost your damage a lot.

For weapon you just want the highest damage crossbow you can find, note attack speed doesn't matter because you're a cooldown based build. In redvale you should get a Tense Crossbow, at lvl 10 you should pickup a Sturdy Crossbow. At lvl 16 you want yo fully invest into a Varnished Crossbow, meaning you'll regal or alch, use 2 artificer orbs and use 2 runes (iron or storm rune). Since you wont swap this crossbow out until lvl 33, you preferable want one with good rolls before fully investing into it. %phys crossbows offer the highest DPS.

For boots you're looking for movement speed, it's an extremely important stat, I would never use boots unless they have movement speed on them.

Body armour is generally the best piece to get defense from, high armour or armour/evasion hybrid is usually the goal, armour is generally really strong in campaign.

Flask: Remember to constantly upgrade your life/mana flask throughout campaign, you can always buy a new one at the vendor when you meet the lvl requirements for the next tier (lvl 10, 16, 23, 30, 40, 50 and 60).

Important: Save all Gemcutters Prism(GCP), these are mandatory for Flameblast swap at lvl 52.

You'll also need to Save a couple of skill gems/support gems for the swap at lvl 52, but this should be easy since you don't use that many skills.