It's a tough question to answer. For one thing, matchmaking is ruined because the player base isn't large enough to support it. You're going to get paired with high ranks. In ranked the shitty part is that win/loss points are super reduced when there's a large gap in ranking, so you're not going to win many points if you succeed, and the S2 will win very few points if they beat you, so they aren't incentivized to play with you in the first place.

As for your second question... get good means learn movesets. Spend time in practice and learn ideal combos. Pick a character and learn what moves are actually useful in the meta. Of the 100-150 moves in a list, probably 30-40% are actually useful in combat and good players will punish you for using the others. You might get a tricky little mix up in here and there but only once as a good player will adapt. Watch tournaments on youtube and study what combos players use. This helped me the most.

Play an easy to use character to learn the flow of things. Sophitia is good because she has decent mix ups, a few strong lows, and fun combos.

Also, learn to step. This game revolutionized movement around the stage, so use it. Depending on your character you can change the whole pace of the game with just movement. Rush in close and then guard, wait for an opening and use a quick attack. Run at a guarding player for *just* a second longer than you think you should and then use a launcher when they block low trying to avoid a grab. When you're faced with a strong offensive string tap <- (back) rapidly several times to make space and then watch as the opponent is forced to come to you. Attacks when moving are slower so you'll have an advantage if you learn what they're looking to do. Use your meter like the resource it is. If you have 2 round wins and have meter remaining, BURN IT. Even if you lose that round you'll get more next round. Never die with meter.