Some players are into gear and, admittedly, I'm a gear head. I have three tubas and a bass trombone. My tubas are a Miraphone 1291 CC tuba, a Rudolf Meinl RM 435 Sb CC tuba, and a Yamaha YFB 822 F tuba. The bass trombone is a Bach Stradivarius.
The "Rudy" is my go to horn. It works well for solo, chamber groups and pit orchestras. It is nimble and yet has a nice punch when you need it.
The Miraphone is another very nice horn and works well for mid-size to larger ensembles. It has a big sound, easy intonation, and is very fun to play.
The Yamaha is similar to the Rudy in size of sound but, being an F tuba, it is more at home for use in chamber and solo work. Between the Yamaha and the Rudy, my choice is based on the tessitura of the rep I'm going to play.
The bass trombone is obviously a completely different beast. I have been playing it since 9th grade. I mostly use it for pit orchestra and big band work.
This is most of the gear I use. Each mouthpiece has a purpose but I will say that I use a standard Helleburg for most of my playing, I have found that the others are very specific and are useful but only maybe 10% of the time. The tuner I use is the Tonal Energy app for iPhone or Android, it is accurate and can read very low notes. I use the main tuner occasionally to spot check, but I highly recommend it's drone feature. I will set it to a pitch and play scales or pieces against it to check my intonation. The real goal is to tune by ear while playing, and drones are an excellent way to learn how to do that. My favorite metronome is the Frozen Ape app. It has settings most time signatures, including mixed meter, and allows you to make any beat in the measure silent. I find that feature very useful as it forces me to keep excellent time and quickly lets me know when my focus wonders.