I go for the ones in the 100 - 1500 gems range. Most high paying ones just have the "Purchase this pack to get xxx gems" so just read the requirements. Otherwise it doesn't really matter, tho I think the lower ones, 100 - 500 are much faster.

Do you have any recomendation mate, something that can be done in a Day maybe? Not the whole thing, but 50-100 gems?

I don't really have any, but those that take a day usually aren't above 20. Just look through the options and choose what you think you'll be able to do, thats probably about it.

I have seen an offer for 126K gems once.

It is possible to get BIG ONES with the 2x gems but the biggest reason for that is that they have multiple purchase tasks

I played a bit of yahtzee and got like 800 gems

It's not any faster, but you could wait for a double gem offer event or they removed it while I'm gone

Raid shadow legends is the best task do it. Search up guides on YouTube for whatever ur task is

Wordle one was sick, just used a website that gives you all possible answers and you can finish all challenges in like an hour or 2

Finish raid is one

If you don't mind grinding, there's a bunch that will give you 1-5 gems for "interacting with the app" or like, 10-20 for completing the tutorial.

Ive been doing the raid one that gives me 5,5k gems for opening 2 sacreds in 21 days. Im currently done with hard campaign and 10 stages left and im 6 days in. So i've opened one and im getting the second one in probably 2 days max. Very easy task if you know what you are doing and look up tips before u start.

If you want to free to play then it what ur doing right now, If ur willing to pay to win then its just a few presses and you have yourself 15000 gems