Basic stuff:
f412, RepDash, f412~Flip
12/34~FFB, njp, 21, f412~Slide
b3/f3~EXFFB, njp, 21, f412~Slide
njp, 21, f412~Slide
Starter~EXKlaw, njp, 21, f412~Slide
f211+3 MB, njp, 21, f412~Slide
b2, f412~Slide
b2, f211+3 MB, f412~Slide
Corner:
f412~FFB, jump back kick, f412~Klaw
12/34~FFB, njp, jk, f412~Klaw
b3/f3~EXFFB, njp, jk, f412~Klaw
njp, jk, f412~Klaw
Starter~EXKlaw, njp, jk, f412~Klaw
f211+3 MB, f412~Klaw
b2, f412~Klaw
b2, f211+3 MB, f412~Slide
After ending most combos, you can do a RepDash to continue pressure/throw out a SFB/Invis/NoxGas.
Blockstrings: 12, 21, 2124, f41, f412, f21, b34, b2
Also, I'm sure many will disagree, but I refrain from doing f211+3 MB unless it'll kill.
Reptile is way too meter dependent and should really save it for wakeups and EXKlaw.
Outdated BnBs.
Here's an optimized summary:
Miscreen:
F412 xx Elbow Dash, NJP, 21, ender (Run if going for a F412 ender)
F412 xx Elbow Dash, NJP, 21, F21 1+3 MB, ender
34 xx Poison Gas, F412 into the combos above
34 xx Fastball, Slowball, NJP, 21, ender(Run for F412)
B2, F21 1+3 MB, slight walk forward, NJP, ender (if going for a F412 ender, you need to run or else some hits will whiff)
B3/F3 xx EX Swipe, NJP, 21, ender
F21 1+3 MB, NJP, 21, ender
Corner:
B2, 21, 21, ender
B2, 21, 141, F412 xx Ender
F412 xx AnyBall, slight step back, D2, F412 xx Ender
F412 xx Anyball, JB1, 21, ender
B3 xx Swipe, NJP, 21, 21, ender
The combos can be made easier by changing a few things like removing a 21 from the corner BnBs, removing NJP from the F412 midscreen BnBs so on and so forth.
They can also be made harder like replacing 21 by F41 in midscreen combos but it limits your enders to F412 enders.
Enders:
F21 1+3
F412 xx Poison Gas(corner fav)
F412 xx Slide(preferred)
F412 xx Elbow Dash
F412 xx EX Slowball
And lastly, my mindset on F21 1+3 is to MB it most if used as a combo starter because you will miss out on big damage otherwise. Using it as a combo filler in F412 is not really necessary unless it kills. The only time it should be used as a combo filler is on B2 midscreen.
But that's just me.
EDIT:
Midscreen:
B1D4 xx Fastball, NJP, 21, ender
Corner:
B1D4 xx Fastball, Slight Step Back, D2, 21, F412 xx Ender
B1 D4 xx Fastball, NJP, 21, 21, ender
Another good ender in the corner is Throw MB if you land a meterless combo such as F412