Pitching Grips And Velocity Help

Question
Greetings Mr. Jon Leicester. I just turned 14 and am going to high school after this summer.

Heres my story: My coach from 8th grade noticed I have a great arm and he had an idea to convert me to a pitcher. I thought I should give it a try because coach should know how to help a person to get the best from a person.
When I tried out. I seemed like I can handle it and learned pretty quickly.
So I start pitching and recorded a 2.60 ERA with 8 strikeouts, 4 walks, 6 hits, 13 innings pitched in 8 appearances.
I throw my 4seam in the high 40s and up to middle 50s.
Even though this may seem slow, people in our league throws as fast as me. I know for high school people should be throwing in their 70s and 80s.

I've tried to increase velocity a couple times and it does not work. Do you have any tips or drills you can show or tell me that can increase my velocity a bit?

The pitches I mastered are the 2 and 4 seamer. I feel a little embarrassed because a pitcher should have more than that.

Can you teach me the slider, change up, and curve ball please? Pictures can help a lot.

P.S. I don't know if this helps but, I can play catcher, 2nd, SS, 3rd, outfield and basically every position but 1st base[If I didn't include it]

If you need me to answer anything else, I will be happy to. [I don't know if I can add additional information after submitting this question though].

Criticize if it will help.

Thanking in advance
- Jacky So

Answer
I say this to everyone who wants more velocity, it only comes with maturity. Meaning, you're only 14 or so, give it time. I didn't throw 90 mph until I was 20 years old. The only thing that allowed me to keep playing until I was 20 was the fact that I could "pitch".
For the time being work on locating your fastball down in the zone for strikes. Learn to command a changeup and a breaking ball. Pitch with your fastball and mix-in the other two pitches if you think that the hitter is "on" your fastball.
If you can learn to pitch now, you give yourself a chance to play beyond high school. That's when a lot of pitchers start to gain a lot of velocity, because their bodies are mature.
As for the grips, check out my website for some pics and some tips for throwing a change-up and a slider (sorry no curve yet).
www.ProPitchingOnline.com/grips

good luck

Jon