The preparations for your first sail should include making sure someone accompanies you, to help you rig... and assist, if it all goes wrong. Other matters worthy of consideration include :
"Fashion" and "image" are words that are not associated with Landsailing - at all, mercifully - so wear what is comfortable, and won't matter if it gets wet or mucky.
Consider where the pulleys are on your yacht, and make sure that you are not wearing loose or baggy clothing that could get possibly get caught in any of the pulleys. If any clothing gets caught in the pulleys, the pulley will jam... and you will capsize.
If there is a pulley behind your head, make sure that any long hair cannot get caught in the pulley.
If it is a cold day, it will probably be colder out on the beach than it is in the car park.
If the beach is narrow - so there is a risk of sailing into the sea - or the beach has streams flowing across it, wear waterproofs. If your beach is very wet, a dry suit might be a good idea … but they cost £250+.
A well prepared sailor who is dry and warm will be able to stay out on the beach having fun much longer than the ill-prepared sailor who is cold and wet.
If it is a warm or hot day, do not be tempted to wear shorts or T shirts. Apart from sunburn, and sand getting where it shouldn't, the sand is incredibly abrasive if you fall out of the yacht - which is a possibility, until you have mastered the basics.
Beaches have a surprising variety of hazards on them, including holes, posts, rocks and broken bottles. You need to be able to see these hazards, hence the need to wear your glasses. Goggles will help keep wet sand - or airborne sand when it is windy - out of your eyes, but wet sand will also stick to your goggles. Sand in the eyes can be very painful, so it is worth trying goggles … but they scratch easier than glasses, so try a cheap pair first.
You are now suitably attired, and ready to sail.
Hopefully your yacht is rigged and ready to go, too.
If you have a Potty Minilandyacht, there are detailed assembly and rigging instructions on the Potty section of this website, which may assist you if you have something similar.
When you buy a yacht, do get the seller to show you how to assemble it.
Most of them are relatively simple and logical to put together, but a little tuition removes the trial and error element.