How do you get better instantly? Buy and fit a good climbing shoe! I don't say you will master climbing, or that shoe, but even with your low, average, or high ability, you will instantly be better.
good shoes, no heels, still climb…
I have climbed with bad shoes, sloppy shoes, Winter double boots, crampons, and no shoes, but I generally climb in the best shoes I can with a very good fit. The better the fit (not the tighter) the better I climb. The shoe is the car, the tyres are the sole, You can't have good performance without the good car and tyres, but of course the driver in the end counts for a lot!
When you put on a pair of shoes if your skin is damp, you will ruck up the skin, and may not even be able to put your foot in a shoe that is the correct size! You need to be able to apply force to tiny foot holds, and whatever is in the way must be kept to a minimum. Not touching the end of a rock climbing shoe is of course a no no-you must touch the end on the shoe, and your toes need to be bent over. If you climb under 6a 5.9/5.10 you can get away with poor shoes and poor fit, but it gets more and more important as you creap up the grades. I won't talk about Trad shoes, or crack shoes, but if it is a hard route crack, or trad I tend to keep the shoe that fits like a glove regardless of other considerations like pain. Pain is how you say in english -temporary.
For years I thought my skill was off, it was in part, but it was mostly my shoes, and the rubber.
I love slippers, but lace ups might give you that bit of extra tailoring. Slippers are quick, Velcro straps are quick, but a good super quick lacing like on the Chimera works a treat.
Heres a pair of other shoes well fitted and being broken in, shoes don't need breaking in, but its real goof if everything is moulded in the correct place.
On cold days take extra care getting into your shoes, skin folds will reduce your effectiveness and cause pain.
In the old days I would take ages to get my shoe to work well, I might even giving it to some one else to wear for a few routes, today you can take a new shoe out of its wrapper and clamp really well. The brand new rubber on the bottom surface needs to become pitted to maximise friction, and sometimes the edge itself needs to be worn a bit to stand on the tiniest bumps and edges.
Forgive me if I am preaching to the choir, but people come to me to improve their climbing, and they turn up in what I term Wellington boots, or Flip Flops.
Once you got the boots, learn to dance, learn to kick your feet up, learn to hook, learn how to drag, toe hook, and move on rubber that is sliding. You have to feel rock in the end, the shoe has to communicate the shape of the hold to you, and you must understand this, and do your stuff, it is an art, but the shoes are the instrument, and you are the musician.