"Megamorph" is a good card to use on your opponent after this card's effect resolves, because it will give your opponent more Life Points than you, and then you can use it to double your monster's ATK.
"Ancient Forest" makes good combination with "Kuribon". When your opponent attacks "Kuribon", you don't take any damage but your opponent's monster is destroyed by "Ancient Forest".
A good combo against your opponent's multiple attacker (Especially if it MUST attack all your monsters, such as an opponent's Monster affected by "Diffusion Wave-Motion"), is that you have "Kuribon" face-up, "Ultimate Offering", "Spring of Rebirth" and "Bad Reaction to Simochi". This will cause your opponent to be in an endless attack loop, as you "Normal Summon" "Kuribon" before they end their Battle Phase by "Ultimate Offering", and every time they attack, they will lose "Life Points". This combo will ensure that you do not lose any "Life Points" for the cost of "Ultimate Offering", while you drain your opponent of their "Life Points" till it reaches 0.