There are three types of climbing: top rope (where your rope is already secured at the top of your climb), lead (where you place protection and rope as you climb), and bouldering (no rope because you're climbing between 10 to 40 feet). And if you get really specific, there are different types of climbing within each of these (free climbing, trad, sport, etc). Climbing is rated by different scales. Although all are different, the higher the rating, the more challenging the climb. And challenging climbs get easier with perfected techniques. And techniques can only be perfected with practice. This is why climbing can get addictive. Invest in the right gear as you advance.
Something comfortable, ideally stretchy and/or durable, that can withstand abrasive rock. Keep in mind you will be in a harness the entire time, so comfort is emphasized.
Two pairs: one is called your approach shoe. It can be as simple as flip flops or as fancy as grippy-soled hikers. It depends on where you're going.
Your second pair are your climbing shoes. Climbing shoes are very specific to the type of climbing you'll be doing, but anyone who is not advanced will do fine with all-purpose climbers. You can often rent these from your guide.
Climbing accessories can be expensive and unless you're advanced enough to go climbing in the dark, it's better to rely on your guide to provide you everything you need. Recommend bringing items you typically use based on the season you're climbing in (see above). However, accessories like harnesses, chalk and chalk bag, and of course, rope are typically provided by your guide.
Lightweight merino wool or cotton baselayer. Baselayers are the tops closest to your skin.
Midlayer or rain shell (sweater or puffy jacket packed).
Shorts. Cotton pants are OK. Cords or denim not recommended.
Sturdy, traditional sneakers or hiking boots.
Minimalist and max cushioned also OK.
Light cotton socks. (I do not wear socks.)
Bandana (it's multi-purpose and always useful).
Bug repellent (like DEET).
Some kinda daypack.