If you're serious about learning guitar this equipment is essential.
I use all of these products in my teaching studio.
Learning to keep time with a metronome is overlooked by most beginners. Keeping a steady beat is essential if you want to be a good guitarist. The Korg MA-1 is a multi-function compact metronome. The "click" sound isn't too piercing and I find it easy to keep time with.
Have you ever noticed how you might raise your right leg (or stand on your tips toes) when you're playing guitar? You do this to bring the guitar closer to your hands and straighten your back. Use a foot stool instead. They're inexpensive and they'll make playing guitar more comfortable.
As picks are inexpensive my advice is to buy a bag of different thickness's. As a beginner you should be using a thin pick (between 0.20mm to 0.50mm) However, as you gain experience you should increase the thickness.
I buy 3 bags of the Tortex picks pictured above at the start of the year, and they're normally all gone by the end!
While not essential, this can save you from neck pain.
When you're learning a song, you spend a lot of time looking at your hands, the last thing you want to do is look away from them to read music. I use orchestral music stands. (because they hold the music securely, unlike cheaper "fold out" music stands)