by Saan
So first, a disclaimer: If you dont like learning and reading the cards in your spellbook, this might not be a game for you.Knowledge of your spellbook is so essential to the game, and is also the reason that first plays of the game can be so horrible for many people.
This is the main reason I advocate building a custom spellbook as soon as possible. This will at least force you to read and know every card in your spellbook(and, for many people, make cool decisions while doing it). In the process of building a spellbook, you will start to get an idea of openings - Generally, the first 4-5 turns of the game will already be in your head by the time you lay the first card.
Playing Mage wars, like playing many 2 player games(specifically war-like games, but this logic also applies to Chess and Go, for example), has a lot to do with how well you can evaluate the state of the game.
Each turn of the game, look at the board and ask yourself: "Am I in a position to win, assuming nothing changes?"
If the answer is yes, you want to do as much damage as possible to the enemy Mage, and reinforce the status quo.
If the answer is no, you have to do what you can to change the game state, which generally will involve attacking the opponents creatures or conjurations in the most efficient way possible.
the 'Yes' answer is an easy one. Direct damage, buffing existing creatures, etc. Pick something that will hurt and play it.
In addition, if you are ahead, do what you can to keep it that way. Use more dispels, Jinxes, shatters, Reverse Magics, and other 'spoiler' cards. Keep them on the back foot. Remember - if you are ahead, the status quo is your friend. Every action you can do to simply cancel an opponents action is a win.
If the answer is 'No', you dont have the luxury to try and play 'spoiler'. You need to do something drastic and unexpected. Is he using a lot of fire damage? Maybe consider spawning a fire resistant creature. Is he relying heavily on Attack spells? Reverse attack or Block can be a good way to swing things into your favor. Is he weenie rushing? Maybe look for options to deal AoE damage or otherwise penalize large amounts of creatures. If you are extremely low on health and it is a rush to kill before you are killed, a healing spell can easily turn things in your favor.
The 'No' answer is tricky, and really is the heart of Mage Wars. Sometimes it is simple as a single creature, conjuration, or piece of equipment the opponent has out. He have a badass angel that is causing you tons of trouble? Find a way to deal with it - Banish and Sleep come to mind if you dont have the ability to kill it, or some sort of Curse Enchantment.