You have several problems. Let's address them one at a time. I'm not going to try to make up false percentages. Instead, I am going to offer you real knowledge gained over nearly 40 years of playing and some real life examples. I hope you will find this helpful.
The guitar's construction it's self has a lot to do with how it will sustain. I have never been impressed with the sound of a Schecter. The Schecter's are not something you hear being played by the kings of sustain. Santana, the king of sustain and tone, started out using Les Paul's and SG's, as well as a Yamaha SG. He now plays a custom PRS, of which PRS offers a signature model.
Santana does not use many effects pedals. he's known to use Ibanez Tube Screamer, Dunlop 535Q wah pedal and a T-Rex Replica delay pedal and then through a customized Jim Dunlop amp switcher which is connected to different amps/cabinets. Santana uses 2-3 different amps to achieve his legendary tone. Most prominently is the Mesa/Boogie, of which Santana's comment during it's development "This little thing really boogies", which in turn, brought the full name of the brand to fruition.
A big factor in sustain is strings. Most of the kings of sustain play with 9's or 10's and change them often. Bad strings are often the culprit of poor strings. Cheap strings will give you a cheap sound. Buy name brands, not big box store specials. If you are going cheaper than Ernie Ball, therein may lie a part of the problem. If you use good strings, how long have they been on your guitar? If they came on it, they were shot before you started. If you can't remember when you last changed them, or if it has been more than 90 days, your strings are dead and a big part of the problem.
How much would putting better pickups in your guitar help? Some. To determine how much, go to a music store and ask to try a similar Schecter that has higher end pickups in to your amp, compared to your guitar with new strings. Is there a noticeable difference? If you can honestly say yes, then pickups would help, but I'm thinking you'd much better benefit from selling the Schecter and getting a guitar more known for it's sustain.
On the question of amps: While "solid state" amplification has greatly improved over the years, Most long time players will agree that the best solid state amp can't ever quite compare to a good tube amp. You can only get natural overdrive from a tube amp, which was originally discovered when the primitive tube guitar amps would get slightly damaged, causing increased gain. Soon, musicians and designers were purposely modifying their amps to create and control the overdrive, which became to be also known collectively as fuzz and distortion. Solid State stomp boxes can emulate this, but it's not quite the same as natural tube overdrive, though these boxes are useful in enhancing it. You're going to get more natural amplifier sustain from a tube amp. If you need more sustain then that, a compressor is the answer.
Fingering and fretboard control are also a big factor. You do not say how long you have been playing, but it doesn't sound like it's been a very long time. You may wish to review some tutorials on bends, pull offs, hammer ons and harmonics. A little technique goes a long way.
So, let's just break this down simply, so that you may find the enlightenment you need.
Strings: You have to have good quality and recently replaced strings to get good tone. You may have to experiment with a few brands to find out which have the tone and response you want. Just stick to the gauge your guitar is set up for, or you will have more problems. Santana, as well as myself, preffer Di'Adarrio .09-.42 ffor electric guitar.
Guitars: Think about the guitars that the kings of sustain and tone use. The guitars most commonly denominated to this are Gibson's 335, Les Paul, SG and their less expensive Epiphone brothers. Fender's Strat and Tele. PRS' SE and Signature series. Ibanez's Artist and many of the Artcore models. If you think of the guys that are known for their killer tone and sustain, like BB King, SRV, Tony Iommi, Jimmy Page, Frank Zappa, Robert Fripp, David Gilmour, Buddy Guy, George Benson, Slash, etc, You'll more than likely find their main guitar listed above.
Amps: You just can't go wrong with a good tube amp. However, you can find some good solid state, with today's technology. But, if you ask most pro's and seasoned amateurs, you can't beat a good tube amp.
On Shredding: Many seasoned guitarists agree that "shredding" is just flash to hide lack of ability and musical knowledge. take some time to understand the theory behind your scales and how comping works with alternate chords and harmony notes in riffs. There is a big difference in a quick articulated solo and shredding. The former will impress more people in the long run. Being fast with your fingers means nothing without theory and technique behind the speed.
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