kmelfina, you won't be winning against a GS any time soon (you need a lot of practice). They have better range, more power, and are fast in every manner possible. Even a crappy one can own a bard since bards lack the range to keep a GS at bay. The only people who can stand up to GSs with ease are folks who have a crap load of HP or evasion. You can also win against them if you know how to camp. Basically, as long as they can't hit you or knock you back, you can win.
In other words, if you have less than 10k~13k HP or less than 50 evasion... You better hope for a good camping/running map.
THEN AGAIN! The use of back dash, counter, or uppercut coupled with high speed may make gunslingers easier for you to kill. Knowing how to use dips in the ground to duck/make them come to you is also another way to beat them.
The Toad/Treasure maps have dips you can abuse.
The Dot Nuri/Treasure/Yong Gyong maps have decent camping spots.
Luckily for you, many Gunslingers seem to be very slow and don't pick up on tactics such as this... So feel free to use it whenever.
LASTLY!(because this post needs to end and I can probably write a novel on PVPing) you need to practice against something other than a GS. Let's face it, a GS is OP when compared to every other class. A blader or TH around your level would be a good sparing partner. As would another bard. Warlords and Sorcerers are more difficult to handle, and most meisters are near impossible to knock back without a well placed ES or strong tier II skill.
If you want, I can PVP you a couple of times on my bard whenever you want to practice.
"He who fights and runs away, lives to fight another day!"