I found Accessories extremely helpful. I am a more-of-a-Success then Love-kind-of-person. That's why People's heart are extremely low even though I made huge progress on the island.
I unlocked all places on the end of Spring, and I started to mine since I unlocked the forest.
After I got an Orichalc, I went to Chen's shop and experience an event with Charlie.
Since I can make accessories, the first thing I made is a Friendship Pendant S. Which gave a 20% friendship boost.
Later on, I found out that I can equip more than one pendant and got accumulated effect (As long as it is equipped in different spot).
When I made 4 Friendship Pendant L, I can instantly made Bachelors's (Since I'm playing as girl) heart Red. How?
1 Friendship pendant boosts 100% friendship, which means if I gave a loved gift (+500 Affection), I got 1000 affection instead of 500.
And if I equipped 3, i got 800% boosts!, that means giving a loved item increased affection by 4000!
When the Heart Event occur, I equipped all four spots with Friendship Pendant L.
When I answered the right answer, which normally gave 3000 affection, the 4 Friendship pendant L multiplied it by 16, resulting 48000 affection increased!
All I have to do next is experienced the other events, and ta-dah! I can propose!
I am not sure about Godhand, Turbo shoes, Time Slowing and Time Quickening, and Earings, but this also worked on other pendants :)
I hope I helped! :D I made all the Main Characters's heart to maximum on Summer first year using Friendship Pendant L ^^