How should I level festust the leechlord?

[Spinalfluids]

I am enjoying his campaign so far but for picking upgrades I am sadly very uneducated. Any advice?

[Lamp]

Think I ended up with extra points to spend on him past where I felt he was done. Wouldn't worry.

Went with his full yellow/magic lines first, blue line for lightning strike and the end one, (usually renowned and feared but for Festus it was different.) Then a bunch of red boosts as well, was using lots of Nurgle chosen and soul grinders so boosted them, easily had enough points for the end line. Specifics on the blue line besides LS and the end weren't really too important, but I went with more souls per battle.

[Falaris]

I do not disagree with Lamp there, although I often play with a slightly higher emphasis on blue line skills.

The only real nobrainer is to pick his special skills once they unlock, the red skill for buffing marauders/chaos warriors/etc, and a selection of blue line skills (because noone else in his army can replicate those). I'd go with lightning strike, replenishment (galipot?), and souls/loot, and the last buff. Ambush and such is less of a priority unless you start fighting skaven. Combat skills are cheaper, but I would save those for last anyway; exalted champions are fantastic at combat if you need that in your army, and magic, you can hire a sorcerer to do for you until Festus gets up to speed on that.

His most important skill - the healing/harming auras - he starts with anyway.

[Imposter]

I am currently on Festus right now. I started with some blue lines(4 I think). I didnt have to worry about Galipot, because i went in and out of replinishment-territory at Brass Keep; i upgraded for recruitment reduction cost.

I went around sacking and fighting armies, playing them manually so I mitigated my damage for wherever I couldn't immediately heal. But I'd also infect myself to give me +10% healing army plague, reinfect myself to give Missile resistance, after I was healed up enough.

Next, I began with some yellow and Magic line, then worked toward 1 red-line skill, so that my army could gain passive experience to upgrade sooner. Which is also something really helpful, like Melee agents do. You should certainly upgrade his 'Special' Yellow line that gives good passives and 'No contact effects' for his army, asap.

Now I have fully upgraded my red lines where I want it, and now I will upgrade toward Galipot, for later.