I like putting power strike, battle fury or force hammer on my thoughtspores. Try to protect them with a block against my opponent trying to blow them out of the sky. I really don't suggest them though if your enemy is utilizing flying creatures.
Force hammer is too expensive, imo. The best spells to put on them have 0-2 range for sure, yet two spores with fire blast deal with most threats. The chance that an opponent will have fliers is quite high, and if a book is built around spores what is the backup plan? Sleep is also quite good to use with them placed as far back as possible, then one can sleep advancing threats, granted that they aren't immune to psychic, which is unfortunately very common. I have not tried stacking them with extra armor, health, and regen enchantments yet but all of that falls over to one sleep spell against them. Attacking a spore to wake it up is nearly a guaranteed impending death. I think they should have gotten a defense like nearly every other familiar. Chock up yet another enchantment to throw on them. Errata anyone??
All in all, the FM needs another familiar or some kind of class-specific method of gaining extra actions. Battle forge is the only solid option in my opinion, and yet so many books run wave or other water spells, and nuking a battle forge is first priority against the FM, imo. Scimitar is quite decent but not exactly comparable. Off hand, I think every other mage has 2-3 methods of generating extra actions, while coincidentally the FM is the most likely to have the biggest strain on her personal actions and needs extra the most.