I will second Thunderfrog's advice. It took me a few tourneys to get my first win (just one game!), even after having played
40k for several years. A few more years to win a
RTT at all.
Laugh at mistakes and ask for advice afterward, over a pint
Enjoy it. My tourney record hovers around fifty percent, for years now, so it is always about fun.
Bring a carry tray to move models between rounds, bed trays or ones from fast food restaurants work well. Printed list, two or three copies
Small, light tape measure
Cigar or maybe
GW box to roll dice in
That ought to do for now.