@Lindsay_jarratt - there’s several options you can pull from:
Ghosts of Saltmarsh - The Final Enemy II, as well as Abyss (from the Board Game Player) both have underwater arenas with cheering, shouting, energetic music, with the Saltmarsh set also including weapons, fighting, different foes (beasts and humanoids), as well as sounds both on the arena floor and the gallery. However, both of these sets take place underwater, so there is a muffled, aquatic sound to everything.
For your open-air arena for gladiatorial games, let’s start with crowds:
Friendly Tavern has some good basic sounds for the galleries, stands, arena holding area where the gladiators may be waiting in the elements: happy rich murmuring, bright rowdiness, echoing happiness, and manly men. These sounds don’t have much reverb. (Though with the Syrinscape creator you could change that.)
For the crowd during fights, there are many options:
Aria Part Protest has the element “angry crowd”, which is great for when the fights really get heated and the crowd is going nuts and screaming for blood.
Baldur’s Gate Encounters has raucous crowd i, and raucous crowd ii, which are both good general crowd ambiance when fights are going on. It also has the elements “cheers” and “cheers & oos & ahs”, which is great when people are rooting for their favorites. It also has “angry crowd” and “angry mob” for very heated scenes.
Finally, Friendly Tavern also has the element “coins and other stuff” for exchanging money when betting happens.
For the arena floor during these fights you can mine Aria Park Protest again: riotous yells, consortium aggression, and thug roars are all great for angry foes during a brawl.
There is a very frequently-found element of “armor foley” (nearly any set with fighting in it has it) that has armor jingling sounds.
Baldur’s Gate Encounters has a plethora of useful sounds: crossbow attack, axe and shield, sword swooshes, spell fighting, barbarian sword fighters, Red Charlotte sword fighter, taking damage, and sword clash woosh.
Tavern Brawl has a variety of punches, thwacks, and ouchy noises for brawling and taking damage.
For more specific weapon sounds, you can pull from Fighter - Male, Rogue - Female, Cleric Spells (Kyra), Wizard Spells (Ezren). These include one-shots of many weapons (staff - which can double for club, greatclub, any bludgeoning weapon, also longsword, scimitar, short sword, dagger both wielded and thrown, longbow, shortbow, hand crossbow, crossbow, and a variety of spells), along with various kinds of armor, walking and running spells, and exertion, laughter, frustration, etc.
For various beasts that may be involved in combat, you can search for almost any creature, though turn off any forest/jungle/swamp/water sounds in favor of the aforementioned crowd noise. If needed, you can pull in winds and footsteps in sand from the Desert set for the sound of people moving on the arena sands.
If you need some sounds for in the gladiators’ holding area/healing room in the aftermath of the fights, Rise of the Runelords - Skinsaw Massacre - Following the Clues has a great “wailing element” of someone in distant pain. The Cultists set (from the Sci-Fi Player) has a great number of useful elements for folks in pain: pleas for help, pleas for mercy, more pain, despair, nearby screams, distant screams, and tortured victim. All of these make great sounds for battered gladiators being put back together (or out of their misery). There is an element called “tools of the trade” in Alien Laboratory (in the Sci-Fi player) which sounds like metal tools being picked up and put down (good for people picking up blades, etc). There is also a “sloshing liquid” element in the Ooze Battle set for dipping rags in a bucket. Vanthampur Villa has the elements of: cooking, fireplace, bubbling hot liquid, and tea kettle, which could be good for a healer at their work. The cooking sounds include a sort of peeling vegetables sound, but could also be stropping a blade for use in cutting bandages, herbs, or amputating an appendage too damaged to save.
I hope that helps!