Every budding bassist needs to own a metronome, a tuner, a strap, a guitar stand and a music stand. Here are ones I'd suggest you consider...
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Vintage Seiko Metronome OR Vintage Tempus Metronome The Seiko SQM metronomes (Tempus is identical) are my favorite to recommend. The older vintage ones are better quality than the newer ones. It's all you need. It's simple, has a good "click" tone, and it's one of the few that hasn't broken on one of my students. I like the dial rather than a push button since you can instantly turn it to any tempo. Get it, use it!
BOSS TU-3 Tuner (TU3) Some tuners come as foot pedals (aka stompboxes). These are especially useful for when you play live. The Boss TU-2 is an excellent chromatic tuner in pedal form.
D'Addario NS Micro Clip-On Tuner A chromatic tuner can detect any of the 12 notes. Chromatic tuners are good for practicing your fretless bass intonation and for non-standard tunings. I wouldn't get anything but a chromatic tuner. This is a good, inexpensive chromatic tuner, and it hides on the back of your headstock. I've tried a lot of these clip-on tuners, and this one responds the best and is easiest to use.
Neotech Mega Strap-Regular, Black (8301052) You should use a strap to support your bass at all times. Get a good, comfortable one like this one. The width of the strap makes a big difference. Get as wide of a strap as you can find. This one may run a bit long if you're shorter.
Amazon Basics Portable Sheet Music Stand - Black A good music stand will make practice a lot easier. This one is sturdy enough to hold your Real Book and isn't easily tipped over.
ChromaCast CC-MSTAND Folding Music Stand with Carry Bag This is a decent music stand for less. This one won't hold heavy books, but any stand is better than no stand.
Hercules Multiple Guitar Stand (GS415BPlus) As I mention in the practice articles, you want to have a lot of access to your instrument so that you practice more often.
String Swing CC01K-BW Guitar Hanger If you don't have a lot of floor space for a guitar stand, hang your bass up on the wall. Make sure you use sturdy wall anchors or screw it into a stud. And, speaking from experience, don't hang it too high on the wall in case it comes crashing down.
Bass Strap Padded Guitar Strap This bass strap runs a little cheaper. Again, go for width and padding. You don't need any distractions while you play, and you certainly don't need any excuses to put down your bass.
Spectraflex Original Series Instrument Cable, 10 Foot, Black If you can afford it, get a good quality cable. These Spectraflex cable last a long time, sound good, and have a lifetime warranty. I know I've had one of these for over 2 decades without problem. Don't go crazy with the length. Shorter cables sound better. A 10-foot cable should be just right.