Recommendations for a returning giga-casual like myself

Starting this late in an inflation league is great, get your early spirit gems and sell them for multiple div, buy all your leveling gear dirt cheap and blast the campaign, you can finish the acts with like 20d easily and most mid gear is in the exalt range. I don't see any reason you can't go from level 1 to red maps feeling like an absolute god.

I play pretty casually with a friend, we go at a slow progression to the point we've yet to actually finish Act 4.

The answer is yes, every time there's a new league/season, just create a new character within that league/season. So in this case, yes, make a new character in the Vaal league.

The main reason why is because each new league/season introduces fun new mechanics to the game. The first time around in PoE2, it was an the Abyss thingy where you found extra mobs to fight, great for getting more loot, XP, and sometimes an additional challenge. Now with the Vaal league, you get a cool 'temple' mechanic that is kind of like a rogue-lite, where you build the map tiles as you go - you can choose to make the room tiles synergize with each other which increases the difficulty of the mobs/bosses but also the increases the sweet sweet rewards.

So why not play with the fun new toys? Worst case scenario, you can choose to ignore it if you don't like it. Besides, your characters get migrated to Standard after the current league/season ends.

Now if your definition of casual goes beyond mine and you actually care about end-game stuff and the impact of the economy (we don't even engage with trading we're just playing the game because it's fun and making fun builds is fun), then yeah, joining late ~~usually means your chances of getting everything super cheap via trade is going to be a heck a lot lower~~ can mean either really expensive or really cheap stuff to trade for.

TL;DR Just create a new character that uses the new mechanics so you have more fun things to play with.

I personally wouldn't bother with fate of the vaal this late, setting up the league mechanic in an optimal way is a full time job that requires a good character/build to be online. I watched a streamer set his temple up and it took him like a week streaming eight hours a day with good rng.

If you want to play normally for a casual wait until next season. Trade is borked jumping in this late. If you dont mind playing mostly as ssf even in trade go for it now. May as well do Vaal league if you do. Theres still a lot of fun to be had for sure.

I started just this week. Did what I wanted in D4, needed something that doesn't quiet handhold. More than a few changes, it's good. Got a month roughly i think till new league so plenty of time to find a build to suck at (I'm horrible come end game)

Very Insightful comments, appreciate it lads and ladies, i will be starting a new char in the league tonight, 🫡

Do you have any particular items/characters in standard leagues that you'd rather play with ? If not, might as well start a new character in temporary leagues.  

Only exception would be if you were a brand new player, because temp league mechanics add extra complexity, and it's not like you would meaningfully engage with trade anyway. But that's not your case.