What is the first Starter lens for your EOS 50D?

Sigma 18-200 OS. Easy for learning and good walk around lens for vacations and with kids. Ive used it on vacations to Hawaii, its obviously not professional grade but thats not what I bought it for. Im pretty happy with it and the price was great. Did not even buy the kit lens.

Tamron 17-50 2.8 is a good starter lens. Very sharp and costs a lot less than the Canon 17-55 2.8 IS. IMO, you don't need IS at that focal point, but having a fast zoom is very convenient in keeping your ISO down and controlling the DOF.

I purchased my 50d almost a year ago, and I got it with the kit 28-135 IS lens- I LOVE that lens! Its very versatile, sharp, and fairly fast once I gained a steady hand. I also ponied up the 70-200 2.8L IS at the same time. I just recently got the 50mm 1.4, and next on the list is a true wide-angle.

i purchased my 40D last month n after reading lot of threads i bought 17-50 2.8(but tht copy wasnt so sharp so i returned it) try to get 50mm1.8 and tamron 17-50 2.8 in 450$ instead of 18-55 and 55-250 400$

For starters the 18-55 IS and 55-250 IS combo is very good advice.

17-55 IS / 70-200 f/4 IS

On a crop it does not get much better then these two lenses.