Hey there, good games today. I'm happy the connection stabilized the second time we played!
First of all, I just happen to know a bunch of stuff about the game, but when it comes to my in-game performance, it's certainly lacking in terms of movement and defense (that's why my ranks are that low). So take my tips with the grain of salt!
I'd advise you to play solo Feng for a while. Playing solo in online is 100% okay, I still do that occasionally. This will help you study Feng faster, and then you'll be able to switch to Leo more to learn her (top-tier team by the way, great pick).
So Feng's beauty is that 95% of his movelist is good, but there isn't really anything outstanding. There are characters like Jinpachi who have 30 ridiculous moves and a bunch of decent ones, so everyone just keeps on using these 30 and it works very well. Feng is different: he has options for most playstyles, but it's hard to concenrate on one single move because you'll get too predictable. What you should do is go through the whole movelist and try every single move. Then you can decide on what do you like more and capitalize on strategies relevant to that move.
But that's very vague, here's a better starting point: 20 very good moves. Before I list them though, you should know that Feng has 3 stances: Kenpo Step (b+3+4), Shifting Clouds (f+3+4), and Backturn b+3~4). For the sake of simplicity, let's call them back Kenpo, forward Kenpo, and BT. Back Kenpo has built-in block, and it gives you access to a couple of good moves, I'll mention these later. Forward Kenpo has built-in parry, and it gives you access to a different set of stuff (back in Tekken 5, both stances' options were the same, and that was pretty bad). Backturn gives you a special 50 damage throw (1+4 or 2+3), a ridiculous 12 frame jab that guarantees a shoulder on hit (BT 1, b+1+2), and a low launcher (BT d+3). Hold d/b to leave Backturn.
f+3,4. Your main whiff-punisher. It's launch-punishable on block, though, so please don't use it for no reason like I do -_-
d/b+3. Long range low poke. Very hard to see. Puts you in full crouch, which means you can follow it up with WS3 (your WS launcher) if your opponent is impatient.
d/b+1,2 or d/b+1~b. Great long range mid poke. Unsafe on block if you finish it, so you'd better use the cancelling option. d/b+1~b puts you in back Kenpo. There's also d/b+1~f for forward Kenpo, but that's risky.
2,4,1~b. 2,4,1 is a guaranteed combo on counterhit, but if you hold b after pressing 1, Feng will cancel the last hit and stay Backturned. 2,4,1~b, d+4 is a good setup.
qcf+1+2. A heavy headbutt that's plus on block. Guarantess a stomp (d+3+4 on counterhit.
d+2. Unseeable low poke with good range.
d/f+1. Good mid poke that's 0 on block.
u/f+1. Evasive punch with a buikt-in sidestep to the left.
b+1. 10 frame open palm strike that guarantees a shoulder (b+1+2) on counterhit.
b+3+4, 3. Back Kenpo into a can-can launcher.
b+3+4, 1. Back Kenpo into a low poke. Puts you in full crouch.
b+1+2. The infamous shoulder. 13 frames, knocks down on normal hit, good range. Very launch-punishable on block, though.
SS 2. Sidestep into a high backhand slap. Good range, puts you in Backturn.
3,3,4 or 3,3,4~b. High, high, low. If the low hits, press 3 to get a guaranteed stomp. Basically a noobtrap, many good players know this strng and will low-parry the third hit. 3,3,4~b cancels the last hit and puts you in Backturn.
SS 4. Sidestep into a low launcher. Unseeable.
d/b+4. Feng's basic low launcher. The combo off of it is kind of hard. You have to hit 2~1 at the right time to get an instant bound.
BT d+3. Another low launcher.
WS3 or qcf+3 (same thing). Mid launcher.
qcf+1. Long range low poke, launches on counterhit. Mix it up with qcf+2. The combo is qcf+1, dash, 1+4, d/b+1+2 B!
d, d/f+1,2 (same as WS1,2). Very important tool to get in. Incredible range. Be sure to not press f, or else you'll get the qcf+1 low.
This list coupled with Feng's punishers [1,1,2; hopkick (u/f+4); shoulder (#12)] will provide you with a balanced set of low/mid/high pokes, low and mid launchers, and a couple of evaisive moves.
There's also an incredible Feng tutorial on YouTube by Aris, but I suggest you don't watch it just yet: it's a shit-ton of information, and it lasts 5 hours. Chances are you might miss a couple of important tips simply because it's loaded with info.
Basic combos. I'll list Leo's assist and Feng's ender first, just use them after B! in tag combos.
Leo's Tag Assault combo: f+3~d, 1,2
Feng's finisher: 3~4,3
Launchers: f+3,4; WS3; u/f+4; Back Kenpo 3.
Solo juggle: d/f+2 f+4,3 B! f+3,4 b+1+2
Tag juggle: d/f+2 d/f+2 f+4,3~5 B!
Launcher: qcf+2
Solo: f+3,4 f+1 d/b+1+2 B! f+3,4
Tag: same
Launcher: d/f+3
Solo: 2 d/f+1 d/b+1+2 B! f+3,4 b+1+2
Tag: f+1 f+1 f+4,3 b!
Launcher: d/b+4
Solo: crouch-cancel, 2~1 B! f+3,4 b+1+2
Tag: CC, 2~1 B!
Leo can use a 5-hit tag assault here, but I don't remember what exaclt it is.
Launcher: SS4; (f+4),4
Solo: d/f+2 f+1 f+4,3 B! f+3,4
Tag: same
Launcher: BT d+4; (3~4),3
Solo: WS1 f+1 f+4,3 B! f+3,4
Tag: same
Launcher: CH qcf+1
Solo: dash, 1+4, d/b+1+2 B! f+3,4
Tag: same
I think those are the most important ones. Every solo juggle taht ends in f+3,4 can be followed up by 4~3. this frontflip will beat backroll and getup kicks. Good okizeme option.
There's a lot more I could tell you, but this should be enough for a while. If you have questions, please don't hesitate to ask. Good luck!