I've played a ton of the pre release version, so here are a few tips till I can tear into the full release. I'm pretty decent on defense, but I suck at offense.
1. If someone jumps at you, MOVE BACK. Dive kicks are nasty, but if they come up short you can punish them. FORCE THEM TO COME UP SHORT.
2. If you can't move back, a well timed jump and throw will grant an easy kill on a divekicker.
3. when fencing, try tapping towards your enemy rapidly. This is called the "Fast advance" and it lets you strike unexpectedly.
4. Learn to disarm. it stops those fast advancers and it can be really effective in tight spaces. To disarm, simply move your sword up or down onto their sword.
5. If you are behind a guy, just run the other way and get a re spawn. Trying to catchup will give them 3 free spawns.
6. If you get a kill, try dive kick running. Do short hops with continuous dive kicks. You can gain a lot of speed and possibly skip a tough spawn (IE, room spawns in the castle)
7. Abuse ledges. If you have the highground you are TOUGH to beat. bide your time. If you are low, try and fake them out. A high sword throw is probably your best bet, but I've seen perfect dive kicks save that situation.