There's this task in my daily hustle:

 But I can't get it to count any profitable deals I make. What does count as profitable drug deal for this task?

Has to be a full load of drugs I believe... I could be wrong though. What are you doing with them?

Ah, that explains it. I always buy multiple drugs to ensure that I have some diversity in case prices change unespectedly.

I suppose I couldn't complete yesterday's hustle for the same reason.

I would suggest always buying/selling one drug at a time, making sure you have a full load.  That way you will complete your achievement right along with making money!

And just check where Barbs/Heroin/Coke is High/Low. Quickest way to make money if you do it locally: travel every five minutes.

For the Hustle, make sure it's a full load. For the lower end drug achievements you have the right idea, buy multiple drugs at varying quantities while flying the districts, you'll get those ticked off in no time. 

i do all my drugs somke all weed and coke i can get my hands on

Buy cheap, sell exspensive, thats thats clue