Nothing is gonna make new people come to this game, at least not a lot of people anyway
The most useful out of these is obviously the auto-whistle
Then probably the ees to item slots
And then market space/free vault slots are probably about the same, with a slight edge to market space
Free vault slots won't do anything besides making people who're already playing save fg from renting the first 25 or however many the free slots would be
The observer slot/s is the most fun one, but overall the least useful imo, this game takes 20 minutes to learn, or 5 minutes if someone just tells you the few things you need to know
What even is there to learn? "Be able to afford good gear." "Click as much as you can" "Afk as little as you can" "Use the right combination of abilities, at the right time" Bam! Done.