Gray

I suggest just giving presents to him occasionally until fall, which is when you get the most money. Then give him his favorite items here's a list of what he likes, also remember his b-day is on the 6th of winter. I know for girls it takes never ending present giving for them to like you. It's normally my goal to get a mate up to yellow by the end of my first year, and to get married by spring of my second.

Loves: Mystrile, Orichalcum, Adamantite, Gold Ore, Silver Ore, Copper Ore,
Bodigizer XL, Turbojolt XL, Veggie Pancake, Fried Rice, Curry, Roasted
Potatoes, Ice Cream, Chocolate, Rice Omelet


Likes: Branch, Lumber, Potato, Egg, Mayonnaise, Cheese, Bread, Bodigizer,
Turbojolt, Wine, Fish, Popcorn, Scrambled Eggs, Cheese Fondue, Dinner Roll,
Pizza, Curry Noodles, Golden Egg, Ketchup, Winter Branch, Winter Lumber

Neutral: Cucumber, Strawberry, Cabbage, Tomato, Corn, Onion, Pumpkin,
Pineapple, Eggplant, Carrot, Sweet Potato, Spinach, Moondrop Flower, Pink
Cat Flower, Blue Magic Red Flower, Red Magic Red Flower, Toy Flower,
Orange Cup Fruit, Apple, Wild Grape, Mushroom, Truffle, Blue Grass, Green
Grass, Ketchup Recipe, Milk, Wool, Yarn Ball, Honey, SUGDW Apple, Rice
Ball, Grape Juice, Oil, Flour, Curry Powder, Stir Fry, Miso Soup, Stew,
Salad, Fruit Juice, Vegetable Juice, Mixed Juice, Sandwich, Fries,
Strawberry Jam, Strawberry Milk, Pumpkin Pudding, Sweet Potato (dish),
Omelet, Boiled Egg, Hot Milk, Butter, Cheesecake, Apple Jam, Apple Pie,
Bamboo Rice, Mushroom Rice, Truffle Rice, Grape Jam, Sushi, Chirashi Sushi,
Jam Bun, Raisin Bread, Sashimi, Grilled Fish, Noodles, Tempura Noodles,
Fried Noodles, Tempura, Cookie, Cake, Chocolate Cookie, Chocolate Cake,
Bandage, Relaxation Tea Leaves, Relaxation Tea, Fruit Latte, Veggie Latte,
Mixed Latte

Dislikes: Green Pepper, Bamboo Shoot, Spa-Boiled Egg, Pickled Turnips,
Pickles, Tomato Juice, Happy Eggplant, Greens

Hates: Stone, Weeds, Turnip, Poisonous Mushroom, Red Grass, Fodder, Chicken
Feed, Fish Food, Food Fiasco, Garbage, Fries Recipe, Dead Weeds, Winter
Stone

Just give her everyday some gifts..

You have to trigger his blue heart event. I found mine on a Thursday, it was sunny and in spring on the 3rd floor of the regular ore mine at 1pm.
His heart wont go up to blue without the event. He will come to your house for the next heart event after that. Once you give him enough presents after that heart event, he will be waiting outside your house for you one morning with a necklace for you ^.^
Hope this helps!

On winter, go to the mine behind the hot spring then dig until you see Gray. Then talk to him, he will tell you that his looking for a silver ore, then go find a silver ore and give it to him. He will thank you then, few days after that he will give you a bracelet or a necklace. (By that time, his heart changed it's color)