Hey I'm a bit of a noob to pedal building and I'm not really up to speed on circuit diagrams but i thought i could modify an EHX LPB-1 for my first project. I want to add more gain to the circuit as well as making it more trebly than it is atm as it tends to be quite muddy. From what I've read changing capacitors is the way to go to achieve this, any ideas on some new capacitors to put in there?
Mesa Boogie Rect-O-Verb
Laney VC15
2x Blackheart 1x12
PRS SE Soapbar II
Line 6 M13, Zvex Fuzz Factory, Digitech Synth Wah, Boss SD-1, Biyang OD-8 (Tubescreamer Clone)
Fixtures <<Click Here
make the input and output caps smaller values. smaller=less bass gets through. stock is 100nF (.1uF). try 10nF (.01uF).

if you want more gain because you want it to distort, build a distortion pedal. in order to get this pedal to distort, you'd have to tweak the bias of the transistor closer to saturation.

use the highest-gain transistor you can find. it'll overdrive all the pedals that come after this booster. it'll OD the front end of your amp if it's the last pedal in the chain. for tube amps, this can be a good thing. SS, not so much.
What I would do if I were you is to get a breadboard and throw the circuit on it. It's a super small easy circuit so it's perfect to start out on. Then you can swap resistors and capacitors to your hearts content. You can also use trimmers in place of resistors so you don't have to swap out a hundred different values. Just turn the trimmer/pot.

Then when you find what you like, change it in the pedal.
Try paralleling the 390 resistor with a 10nF cap or smaller, too, this increases treble response.

For the input cap, try 22nF, this puts the low frequency roll-off at roughly the lowest signal your guitar can pass, ~82Hz. 10nF is roughly double this, 160Hz. Capacitors also come in 15nF readily available.