The game already has a built in function for giving handicaps.
If you want to disadvantage yourself against the opponent, simply lower your 120 spell points... build an 80 or 90 point one. If you want to give the advantage to an opponent, increase them to 150 spellpoints or so. Its simple, and the opponent understands the advantage you are giving them by simply showing them the mage card. You dont have to "play down", and then when they are acclimated they can just start playing a regular book. This also teaches a value for spell book point effeciency very early on.
I like the spellbook approach to handicapping: but giving them more spellbook points can just give them more stuff to choose between, which can make it more daunting! So limiting your own stuff might be easier.
In general, Magewars is easier to handicap than many games as you have the pre-game of making books. When I play against people who I tend to beat, I'll often play a thematic but sub-par mage (e.g. a Dwarf Warlord with only Dwarfs as creatures), which then means it's more challenging.
There are also some specific tricks that I just wouldn't use against a new person: basically, stuff that they probably don't realise you can do! So basically anything involving enchantment transfusion for instance.
Finally, frustration isn't just about winning/losing. The swiftest change I've made was playing against a newish person when I brought out a Priestess who had armour up to the hilt, plus veteran's belt, plus aegis: he basically couldn't put any damage on her, and I had cheap heal anyway. The issue there wasn't that it was overpowered, so much as if you didn't beat it, it was boring. A bit like the old Magic the Gathering 'permission' decks where you countered everything the other person did: it just isn't a fun game unless you've got into that sort of deck design meta.
