Once you go to the blossom festival and buy flowers there, start gifting them to the girls. The flowers have a VERY high chance of success with the girls, no matter which flower or which girl. They are more expensive than the other gifts, at an average of about 30,000 coins apiece in addition to all of the event tokens, but they are useful for maintaining a relationship.
Just as important as what gifts you get the girls, though, is WHEN you give girls the gifts. Give them as soon after the cooldown is over as possible. Once you pass 1 1/2 hearts you can then receive gifts from them, and as the hearts increase, the girls will give you better and better gifts. If you don’t want to wait for the cooldown period to be done and you want to give them the gifts right away, then set the time ahead on your phone or tablet by however long the cooldown is, then go to the game and gift them again.
One of the absolute surest ways to maintain a long life within a level is to maximize the self-healing that you can do in the middle of battle. To do this, switch your charge attack to Life Steal, equip something that has a chance of healing you when you deal damage (such as a Crimson Crust at five-stars), and use your shield and charge attack at the same time as often as possible. Use your potions literally the second that the cooldown period ends for them, to keep your healing going to counteract all of the damage that you take.
Once you unlock the Loot Luxury, use it in old village areas to earn GIGANTIC quantities of items, which is especially useful when those items are needed as trade bait for a merchant or as gifts for a girl – or, of course, for evolving a piece of rare equipment and upgrading your potions for massive healing.
Each different color potion has a different side boost that goes along with its use. The red one will provide a temporary boost of defense, for example, while the green one will provide a temporarily boost of speed. Go to the potion upgrade screen and tap and hold the green vial icon, which represents the bonus boost, to see what the boost is for a specific potion.
Once you hit rank C-5 and above you will start to earn offline gold and experience points. The higher the rank, the more you will earn for the amount of time that you are away. If you want to earn the offline stuff immediately, then go to the date and time settings and set the time ahead, then come back to the game. When the time is reset back to normal, though, you won’t earn any offline stuff for that time a second time.