If you are still learning or mastering the basics of M&B combat, battle/siege are not the most efficient way to improve. Spectating a good player is a great way to pick up on little things that make the difference between an okay player and a good player. Spawning and fighting won't teach you much mechanics-wise. Your death will be quick and brutal, but you can improve your battlefield awareness. Note where your teammates go. Check behind your back frequently. This will cut down on a lot of the "bullshit" deaths where you get backstabbed or forced into 1v10 combat.
If you want to get better at melee combat, the duel server is the place to be. It's easy to find someone who will help you practice blocking/footwork/kicks/nudges etc. For ranged, the only thing I can suggest is singleplayer for aiming practice. It took me a long time to learn how to properly aim in M&B, and if I don't play ranged for a while I do really poorly when I jump on my ranged alt.
