Spell selection is pretty important for magi. Fortunately, you're a book caster can change when something turns out not to work too well. Things that have worked well for me:
- I took the Force Fang feat which gave me a better focus spell with which to recharge spellstrike than my school spell (the shooting star for starlit span).
- I took a wizard dedication and spent a lot of feats on it, got a ring of wizardry and endless grimoire, which gives me a whole lore more spell slots.
- I got a lot of Spellhearts to gain more cantrips. I like to have all possible attack cantrips so I always have the best tool for the job.
- Later on I also got Expansive Spellstrike and Fused Staff. Those two feats turned out to work well together, because a lot of the good spells on staves need Expansive Spellstrike. Also, Starlit Span and Expansive Spellstrike allows you to place line and cone spells in very unusual directions which makes it easier to line up multiple enemies.
Note that most of the magus focus spells aren't useful for use in spellstrike. They're kinda the opposite: useful to combine regaining spellstrike with another action. It could be useful though to get some spell attack focus spell. Very popular nowadays is to do that through a Psychic dedication, because they have very powerful options. Other ways are through cleric or champion dedication and then using Fire Ray from the fire domain (initiate).