Okay - you have a court, you have two teams, you've talked Aunt Agnes into being your umpire, and a handful of friends and relatives have been cajoled to come along to cheer you on.
What else do you need?
Excluding the ball (which is covered elsewhere) and the stumps, the rules require two other pieces of equipment.
The first of these is the bat.
Because the ball is considerably lighter (and somewhat softer), Indoor-cricket bats need not be of the same quality (or cost) as outdoor bats. Most players seem to prefer a light bat, although many outdoor players use their outdoor bat for indoor cricket. It is obviously a matter of choice. Centres do provide cheap bats for players to use, but having your own allows you to get used to it and, in theory at least, make batting easier (I have a theory about theories, but that too is another story). The bat's dimensions are covered in the Rules section.
The next piece of equipment required by the rules is gloves.
Each batsman MUST have a glove on each hand when batting. They need only be light cotton gloves, and centres usually provide these on a communal-use basis. However, if you are facing good fast bowling, standard outdoor batting gloves are recommended. The fingers and knuckles on standard batting gloves are fully padded - a good idea against a fast, new ball. Good quality leather batting gloves can be bought quite cheaply and should last several years.
Wicket-keeping gloves are of course worn by the 'keeper, if they so desire. They are specialised gloves, and many indoor cricket wicket-keepers prefer to use their own - regardless, centres always supply them for less-fussy players' use.
Now, although the rules don't specify it, there is one other
absolutely essential piece of equipment, especially (but not
exclusively, I am reliably informed by many female players) for
male players. The male version of this is almost universally
known as a "box", the female version more gently a "female
protector".
This handy little bit of plastic serves both male and female players especially well by protecting that most puritanically vague euphemism, the "groin". More correctly termed a "protector", it is also essential you buy your own.
Never, never, NEVER lend or borrow a protector - there are some things mates simply shouldn't share . . I'd probably add "never share your mouth-guard either".
A protector will only cost a few very well spent dollars. NOTE: I have seen several instances of (look away Aunt Agnes) . . . split scrotum in indoor cricket due to male players wearing very loose protectors . . okay, due to wearing loose protectors AND getting smacked thereabouts by the ball. I strongly recommend players wear tight underwear to hold the protector in its proper place (many players wear two pairs of undies for that very purpose). For the men, it doesn't take too much imagination to think of the damage possible if a loose protector allows just a little bit of one half of those it is meant to protect to peep out the side; and for the women, well, I'm assured it's just as dangerous even if not as seemingly amusing to their teammates as when it happens to a male . . . brings tears to my eyes just thinking about it. You can look again now Aunty.
Chest protectors are a great idea for the female player, and I'm informed they are becoming increasingly common. And yes, I have known at least two male players who regularly wore chest protection.
Knee-pads are a great idea, especially if you are the sort of player who dives around a lot. They are cheap and readily available, being used in several other sports (volleyball especially). While less common, some players also wear elbow-pads. And if you're facing fast bowlers, especially if you're ever given shiny brand new balls to play with, I'd strongly recommend wearing hockey-style shin-pads too.
Mouth-guards are a very good idea too, although very few players seem to use them. In terms of the damage and dental bills they can prevent, the few dollars they cost is an astoundingly good investment. For children, I'd go so far as to say they should be compulsory.
Protective eye-wear is also available, of the sort designed for squash players. However, because the ball is so much larger than a squash ball, severe eye-injuries are far less common in indoor cricket than in squash. In all my years playing and umpiring indoor cricket, I have only known a handful of players who wore protective eye-wear. ... and I can only recall three players wearing goalie-type face-masks - two of them were wicket-keepers (one of whom went on to play 128 Tests and 244 ODIs for Australia), and the other one, with whom I played for many, many years, was just an old sook. So that's about it ... a bat, gloves, a protector, and perhaps (strongly recommended) a chest protector, mouth-guard and knee-pads. And if you use the equipment provided at the centre, you would only have to spend a few dollars protecting your "groin"..
. . . one last word related to the above:
As a player who used to dive around like a madman (when I was much younger I must add), I very very often lost skin from my knees and elbows/forearms. I quickly learned how to save myself much pain on those occasions, as follows:
I would thoroughly clean the wound as soon as I could, then I'd cover it with a sterile dressing (a Band-Aid if the wound was small enough), and then I'd forget about it for at least a week. Always always always, I would leave it covered! None of this "let it breathe so it can dry" nonsense. I'd keep it covered with a sterile dressing until it was healed (unless of course it becomes inflamed, meaning infected). Keeping it covered prevents the wound from drying out . . . in other words, there was never a hard scab to painfully break every time I bent my knee or elbow. And it also meant waaaay less scarring. Worked every time for me . . . well, until my knees and elbows and forearms began complaining so much that I relented and started wearing knee and elbow pads.