I’ve long been a fan of musical instrument accessories such as music stands, tuners, metronomes, winders, etc. What guitar nut wouldn’t love to collect all these goodies? In all seriousness though, most or all of this stuff is very useful and even essential.
For most musical instruments, accessories help to enrich the experience and bring the musician the best tools to keep their skill building moving forward.
The metronome is by far the most important tool you will ever purchase after your guitar or whatever instrument you play on. Learning your timing is crucial and many folks just can’t keep in time without a beat. The beauty of the metronome is the ability to change the speed of the beat up or down. If you are practicing a fast-paced song, such as Battery, you would start at a comfortable beat like 80 bpm and then work your way up to 200+ bpm while keeping your form perfect.
Back in the old days we would tune our guitar instruments with a tuning fork to get our “A” note and then tune the rest of the strings from that starting point. But, those dinosaur days are gone and one of my most used music instruments accessories is the electronic tuner. You can either plug it directly onto your guitar or if you’re playing plugged in you just need to turn it on and in seconds all 6 strings are in tune.
I even have amp modeling devices that plug right into my laptop through a software interface. For playing at home there are no other musical instrument accessories that come close to the usefulness of these devices; they have built in tuners as well. They are especially great as you are playing through headphones and although you are hearing the roar of an electric guitar, anyone else nearby will only be hearing your unplugged playing 
.
For doing your own maintenance such as restringing, a winder with a built-in cutter is essential. What would take you half an hour to do by hand can be accomplished in a fraction of the time with a winder. One word of caution though, as you’re nearing your desired string tension, it is a good idea to finish up with your fingers as you have better feel this way. You don’t want to break one or more of those brand new strings or worse, break the neck of the guitar.
Some music accessories are not entirely necessary so if you’re on a budget don’t just go crazy buying everything in sight if you don’t really need it. The metronome and a tuner are the bare bone essentials. Other music instrument accessories such as a stand for your instrument or the sheet music can wait. Spend your extra money on good strings for now.