Slayers Try is the third season and can be watched alone, but is better after Slayers and Slayers Next. It's a great classic anime about sorceresses and swordsmen. It's full of adventure and lots of comedy.
Still one of my all time favorites after all these years. Try is one of my favorite seasons because it introduces Filia Ul Copt and it has one of the most developed plots. Xelloss/Filia forever!!