I’m seeing opposing things online about it. Can a character with Shillelagh cast it while also holding a shield? I’m trying to play a wis based hollow warden and want to use Shillelagh and a shield before I pick up war caster at level 4.

Second question, if I can cast it without war caster, is there a better wisdom increasing feat I should pick?

A staff itself can be a spell focus, so yes.

Ranger has no issues because they can use a druidic focus, so their staff works. The popular Eldritch Knight Shillelagh and shield build is the one that doesn't work RAW.

For you, War Caster isn't needed, and there are definitely more fun wisdom options. Just depends on what you want to do.

You must have at least one hand free to perform the somatic gestures of a spell

Sweet, thanks for the reply!

Thank you!

There is a subclass in the 3rd party Crooked Moon game that gives a Druid a free Shield when they use Shillelagh to make them more of a martial class. Circle of the Old Ways

Rangers can use any druidic focus as their spellcasting focus, this includes a wooden staff which also functions as a quarterstaff.
Since Shillelagh requires a material component you can cast it using your staff, so you don't need a free hand.

I will also note that the Topple mastery (which the quarterstaff has) scales with the ability modifier used to make the attack (in this case wisdom) so it's a good option.

That’s cool! I’ll check that out!

war caster doesnt solve the issue either for EK fyi

You can use a Druidic Focus for your Ranger spells. If you get Shillelagh via Druidic Warrior, it counts as a Ranger spell. If you get it via Magic Initiate it doesn't and you'll run into problems if your DM plays components RAW.

Thanks! Topple sounds great for what I want to do

Oh I didn’t know about the divination feat. I’ll def look into it!

For sure! And do look into the arcana unleashed feats, they're nuts and would give a ranger access to a ton of spells they wouldn't normally get

Spell Component Ring, from the new arcana unleashed book, is the definitive answer for this kind of stuff. You can bypass the shillelagh material component problem, if you can't use the quarterstaff as the focus to cast shillelagh.

Most of DMs don't care about this, tho.