The heaviest tripod that you can carry would be my recommendation. If you are going to use your field camera hiking or backpacking, then of course a graphite one would be the one of choice. That being the case, try to find one that has a hook on the bottom of the center column so you can carry a bag into which you can place a heavy rock(s) (if available on location) to help stabilize the system (believe me, you will need to someday!).
For studio or home use, look for a used Majestic or really heavy Manfrotto - the heavier the better.