Me, right now: working on Mountain of Faith lunatic no bombs and generally getting more consistent at Double Spoiler
Me, a year ago: working on Mountain of Faith extra no death no bomb (and just clearing lunatic for the first time!) and unable to clear all the scenes in Double Spoiler
Me, 2 years ago: trying out and barely making it through IN lunatic with max lives and unable to get beyond Stage 3 in Double Spoiler
Me, when I first started out: THIS GAME IS IMPOSSIBLE EASY MODE IS NOT EASY AFDSFADSFDASFD
The only way to get better is to keep playing. Become more familiar with the patterns, both the common ones that show up all the time and the specific ones to each game, stage and boss. Get comfortable with the movement speeds and make the character an extension of you, so that you aren't thinking about the inputs to move the character but simply moving the character.
Most importantly, don't be afraid to use every resource at your disposal. Continues for unlocking stages? Do it. (I did it with UFO lunatic, and though I still haven't cleared it's mostly for lack of trying, as I can definitely do it off the practice runs of each stage-without continue-spamming to get through the later stages, I would be nowhere near clearing).
Bombs? YES! The game gives them to you for a reason. If you get overwhelmed, use a bomb. When you run out, try to dodge. Save no bomb challenges for when you're more familiar with the game and can dodge its patterns, or stage practice where there's nothing to lose for trying to dodge.
Higher difficulties, patches to increase difficulty or gamespeed? If you feel up for it, yes! Trying to play slightly above your skill level definitely helps! I started out with IN with score files already unlocked and the first big things I did were all geared towards spell practice-which did include unlocking a few last spells to unlock last words and such. Was I hopelessly outmatched? Yes. Was it still fun? Yes, yes it was, and it was a valuable learning experience.
Above all though, try not to get too discouraged or offput by difficulty spikes.
You have to practice. A lot. True!
Unless you have natural talents, there's no way around it. False! You can just play for fun and not care about results, and those with natural talents for the games still have to hone them with practice!
Use stage practice, watch replays of people better than you, realize your mistakes after you make them. True! This is helpful, thogh I find people around your skill level to be a bit more helpful than watching, say, Jaimers LNB DDC for how to handle certain parts.
Do not spend credits until you are knowledgeable of every part of the game. Horrible idea. Just play the game and get a feel for it. Besides, all you're putting in is time, and honestly, is that really such a big deal? (also, when I cleared Subterranean Animism on lunatic it was the first run I had that didn't die before midboss Parsee-I was flying blind through all of Stage 3-6 and cleared via knowing when to bomb and when to try to dodge)
Short version: Yes, these games are hard. But they're very rewarding if you put a little time into them. Welcome to the community