I've been playing Tibia for 12 years by now and have used regular hotkeys on F buttons and currently I use (not sure if I can mention brands here, this is my first response on TibiaQA) a really nice mouse from Razer (Naga Trinity) which gives a huge advantage since it has 12 buttons on a side panel plus a few more buttons on the top area.
Although I am main sorcerer, druids aren't that different. This is more less the configuration I had before buying my mouse:
F1 to F4 - Healing spells. Since mages have a lot of spells, you may run out of buttons, so depending on your level and magic level, it could be good to leave one of your healing spells out. In my case, I rarely use Ultimate Healing since Strong Healing heals more than half of my HP. So, having two healing spells for you, and then Mass Healing and Heal Friend.
You can also use Shift + F1 - F4 for Strike attacks (Ice Strike, Fire Strike, etc), so by doing this, you just need to press/release shift to attack and heal yourself or heal your allies.
If you decide to try this configuration, I would recommend you also configure a button (Tab for instance) to Auto-select the creatures you will attack. This way, once you want to target another monster, you don't need to take your hand back to the mouse.
Last but not least, if you can afford a gaming mouse with customizable buttons, it will truly improve your gaming experience.