Remember, G-spot stimulation is not for everyone. Some women don't get anything out of it, while others crave it. There are some theories that the G-spot is simply the base of the Clitoris and we are only stimulating the clit indirectly when stroking the G-spot.
But I wouldn't know cause I've never experienced it. Ladies? ;-)
As for learning how to masturbate better: No pun intended, but if you stick with it, these things come in time. The brain is really good at figuring out what feels good, and losing what doesn't work so well. Sex feels good for a reason; we are SUPPOSED to like it. So, like anything that we are driven to do again and again, we LEARN how to make it work better over time. You might consider shifting your focus away from your clitoris for a bit, and onto somewhere else beyond the obvious -- nipples, belly, inner thighs. Slip a finger or two inside yourself to massage your G-Spot. It is the rough-feeling place just at the upper inside of the front end of your vagina, kind of "behind" your clitoris. It sort of feels like the roof of your mouth. This rough spot is meant to excite both you and your lover (Nature is assuming it's a male here) by stimulating the coronal ridge of his penis to bring him to orgasm so he will ejaculate his sperm inside you. But you can massage it yourself to lovely, intense effect, and bring yourself to orgasm from this alone. In concert with your clit and nipples etc., you should be able to get there on a regular basis.
By the way -- a note about squirting. Not all females ejaculate to that degree or in that way. If your body IS capable of that, it will likely happen as you achieve your orgasm. As you reach your orgasm, push "out" and "down" as if you were trying to pee. (It helps to sit with a towel under your buttocks.) When you orgasm, you might just squirt! That fluid serves to lubricate the area (and the penis that might be entering you) to make things go a little smoother. But it is not absolutely necessary, as the vagina manages to lubricate itself without that, and not doing so is not a failing or a shortcoming in any way.
But remember, your orgasm is not just driven by your clit (or your nipples, your belly button, your anus, your mouth) or even your G-Spot. In short, the physical sensations you create with your fingers are only a PART of what goes into your orgasm. Most of it is actually in your head. Your BRAIN, your MIND really drives your body when it comes to orgasms. The brain takes the sensations you create and mixes them with memories, fantasies, images and other stuff in your mind to begin the process that culminates in orgasm. A lot has been written about that, here and elsewhere, but it bears repeating. Orgasm is a delicate dance you do with yourself. Lots of things go into making it happen, including strong feelings of love for a partner. Lots of things can also get in the way -- subconscious fear of punishment, thoughts of being "bad", etc., even desires for a particular, absent partner can distract you or detract from the pleasure you want and deserve. You may need to give yourself PERMISSION -- the freedom -- to have and enjoy the screaming orgasm(s) you deserve.
So, keep exploring the sensations your body can create, and Good Luck!