Post-purchase

Now that you've acquired your dream guitar, what do you need to own to keep your needs in check? Or are you that type of person who would only purchase stuff on a needs-only basis?

First & foremost, you need an amplifier. However, the philosophy of amplification today had been displaced by amp simulators residing in the computer. Simply put, it pretends to be an amp so that when you plug into a computer, it receives your signals & processes it to make it sound like you are playing through an amp. I'm not compelling you to get an amp & tread the purist path because the simulators today are darn good imitators. The latency issues had been dealt with along the way & this, in my opinion, makes amp simulators more respectable. Let's move on.

The items on this list are neither definitive nor final.

Essential

• Tuner. Everybody needs a tuner unless you have perfect pitch. If you play acoustics without any electronics on board (a tuner is a common feature), a clip-on tuner is compulsory acquisition. The electric players are better off with pedal tuners (just my opinion) unless they are pro players who need to prance around on stage most of the time, away from their pedalboards. I've tried app-based tuners; not too bad but it gets distracted easily by extraneous noise. 
• Cable. Never be content with that complementary cable that came with your guitar. The ones that came with my Ibanez some time ago ended up being radio antennae. I heard a phantom Michael Jackson singing through my amp once, so there. Invest in a good cable which are very affordable today unlike in the 1990s when I started out. Preferably, get one with replaceable plugs & OFC wires. To me, a good cable makes or breaks your interest in playing.
• Picks. Try different picks along the way. Try different pick materials, thickness & shapes. These are the pick factors that would define your picking hand movements & eventually your playing precision. I started out with thin picks because those were given to me, I didn't know there were other picks out there which were life-changing (they still are). Also, what works for others might not work for you. Till today, I'm still trying out picks.

Good to have

• Strap. Even if you are a bedroom guitarist, you should at least try playing standing up. There's a marked difference in playing position & posture when you play standing up with the guitar strapped on, the main factor being the fretting hand curvature. I discovered that the standing position frees the hand from excessive stress (that impedes movements) simply because the guitar, in its strapped position, forces the player to straighten the forearm.
• Guitar stand. Do not lean your guitar against the wall, cupboard, table edge, etc. because the chances of it toppling over & breaking is very high. Also, not all guitars can be placed flat on the floor due to its angled headstock (eg. Epiphone, Gibson). If you have to leave your guitar out till the next playing time, get a good guitar stand, otherwise, keep it away in its case / bag.
• Polish cloth. Please, please... wipe down after play. If you don't believe in polishing, just give it a wipe down. This removes moisture & grime off your instruments. You won't appreciate this routine until your guitar's bridge is corroded beyond cleaning or your guitar's electronics get messed up entailing in repair costs. If you do not believe in buying a dedicated instrument polish cloth, use an old t-shirt which works equally fine but it needs to be cotton, no compromise.
• Polish fluid. The job of this fluid is actually to remove grime / oil off your instrument, a good shine is a bonus. This often goes unnoticed till its accumulated significantly on your instrument making it look really repulsive. At the very least, it will affect your instrument's resale value if you are considering selling it off.

Pics: Swee Lee / Dunlop / GC