On Harvest Moon Tree Of Tranquility if you want to marry Gill...?

Lets see.....

I'm fairly sure you have to have your house upgraded to level 2 (?) which was a requirement at the beginning of the game to get the second half of the goddess tree quilt

Also, to marry I think the person must have 8 hearts for you since when a person has 8 hearts, the mayor will come and tell you about the blue bird of happiness (or whatever) and then a little while after that the bird will come and you can find the blue feather

gahhh, sorry its a little confusing >/////3//<; hope it helped a little

You have to upgrade your house to level 2 to get him talk to you again. When this happened to me, I got super annoyed because I couldn't give him anything. Just upgrade as soon as possible then get to 8 hearts. When you do, the mayor will come to your house and tell you about the blue feather. A few days after that, you'll see the blue bird when you walk out of your house in the morning. When that happens, go check Caramel Falls everyday. After a while you'll get a cut scene where the blue bird flies over and it drops a feather. There you have a blue feather.

Note: You can only propose to someone if the town hall is open because you'll go there to book your wedding. I tried that and Gill just said "Oh...a blue feather?"