First step get all 3 of them to the same level try and keep them at the same pace and don't faver one person step 2 make sure to have lot of coffe at the start of the game before you learn how to reserect fallen allys even after she learns how to make sur to have a pletifull suply of coffe step 3 make sure to all ways upgrade gear and to get your gear stronger step4 look every where for chests most homes that you can not enter you can steal from and get stuff and allso look behinde objecs for there may be a chest step five the most inportant step of all have a good time playing the game
Well,you need sort of a balance,upgrade natalie´s armor(as she has poor defence but great magic resistence)Upgrade Matts´s weps and armor,as he is litteraly the meatshield,he can do one of the highest damages on the game,while for lance,hes balanced,id upgrade his armor tought,he might have defence,but it seems his health is quite poor.
First learn skills that you can always use. For eg. Revive is very useful if your ally dies. Then Try to divide the elements like fire, earth etc. between the three and make each one of them an expert in that particular element. Also, try to complete quests asap and get equipment.. They come in handy. Also, scan your enemies and use equipment that is suitable for engaging them. For example, if you are facing water based enemies use lightning based attacks and wear water based armor. Don't use fire attacks against them.
P.S. have a lot of coffee with you especially when facing big enemies.