If you do the activities via the side missions it can feel repetitive, but I've stumbled across enough of them that I've done as and when I wanted that sometimes I only have one or two to do for a side mission.
There are tips and tricks to getting gold on some of them very, very easily.
For insurance fraud, jump up in the air, slump while you're high up, and you can basically cartwheel around the whole map and hit gold in no time.
For on foot mayhem, get the tornado upgrade to sprint, and then just run around the area (preferably along the sidewalks) and all those lovely fences etc. that you whip up behind you crank up your total to gold in seconds.
For TK mayhem, just pick up one of the ball things, and hold it out in front of you while you do the same.
The lightning upgrade for telekinesis is very useful for the fight club things - pick up the people and chuck them at other people, although I absolutely hate that activity and am yet to get gold. I've got gold in everything else now I think though.
As ever, I find the carjacking thing boring as hell, and one of the 'easy' rated Blazin' challenges is a cunt - the one at the airport - I keep getting lost.
I think it's probably a better game if you get a lot of the references. As a staunch Mass Effect trilogy fan, it's no surprise I think this game is amazing. Half of it is ripped directly from Mass Effect, and that's even before you consider Keith David. That said, there are no doubt many, many references I'm missing completely, but I still love the game.
One of the moustaches you can pick is called 'The Detective.' Am considering recreating Suchet's Poirot and seeing how he handles being leader of the Saints