Any sotwuer or any tool you recommend as a strategy for playing poker
GTOWizard is pretty good, has a lot of preflop spots for free.
If you will have a paid GTOWizard you won't technically need a solver, but if you want one for experiments you can take PiOSolver (which is paid). There are some free solvers out there if you want to go full free mode, aka TexasSolver (crashy) or WASM/Desktop Postflop (quite decent), but they lack some features that paid solvers have.
Also I recommend having Equilab for researching
equity (free). PocketSolver is another free equity research tool that has some useful features that Equilab doesn't have, but the interface is clunkier than Equilab's making it annoying to use.
OpenPokerTools is a fun thing to play around for postflop statistics.
Also if you are an MTT grinder you can look for free ICM calculators, like the one on holdemresources. There are also ICM solvers like ICMizer, but I haven't used it.
If your room allows HUDs you should probably look for one too.