Hmmm...I presume, you wish for the boyfriend to propose to you, right? Okie-dokie! On it. Anyway...
I agree, winning in gambling is challenging at best, however, a boyfriend can propose even BEFORE you complete all 8. Try this:
1. Try to buy all Rare garments.
2. While at it, tan more than 3 times.
3. Take more pictures. About 15 will do in total.
4. Have some more dates.
5. Win more parties.
That should hopefully do the trick. I am not sure how many more things you will need to complete, but I have had a personal experience of a bf proposing while I had only 7 completed, but at the same time I had more than necessary items done in other lists. Under 20 in each case should be fine. Do the easiest ones first: pictures and others. We also have one of the guides here how to have a better chance at win if you gamble. http://itgirl.wikia.com/wiki/Susie_Kaehler%27s_How_to_Win_In_a_Casino:_The_Hi-Lo_GameDo check it out. :) Good luck! Hope it helps!