There are good reasons to avoid pools, but fear of a lawsuit isn't one of them. If you do get sued, congratulations. You'll almost certainly never be sued unless you win a sizable amount. That means you're a winner. Other than never winning, you can't do anything to guarantee that you won't be sued, but you can make it unlikely and you can make it a virtual certainty that you won't lose. There are really only two issues to be concerned about. One is who is a member of the pool, and the other is who owns the winning ticket(s). Most of the rest is just figuring out the little details, and as longas everyone is in agreement you probably won't have any problems.
First, everything has to be in writing. Every member should have an original copy of the agreement. Every member should sign every copy and be witnessed by a notary.
Second, don't even consider allowing people to be in some drawings, and not others. You'll just be begging to be sued by somebody who will argue that it is your fault and not theirs that they were unable weren't allowed to participate, or they'll argue that they did participate and you're trying to cheat them out of their share. Even if you win you'll lose the legal fees. The pool can choose not to play until the jackpot gets to a certainlevel, or to play for every drawing, but make sure it's spelled out inthe agreement. If you still want to allow people to play or not for some reason, I'd suggest one of three options. 1. Treat each drawing as a separate pool. I would never consider the nightmare of dealing with that headache, but to each their own. 2. Have the agreement written by a lawyer. This will be expensive, and still won't guarantee that there isnt a legitimate dispute. 3. Reconsider, and require that every member participate fully.
In addition to listing who is a member of the pool, the agreement should detail the procedure for removing somebody from the pool. That proceduree includes reasons for dropping somebody and how they will be notified. I'd suggest that they be notified by certified letter, sent early enough to ensure delivery before the first drawing for which they will be dropped. Another certified copy should be sent to the administrator, and it should be kept unopened until such time as it might be needed. Better still, swear an affidavit that the member has been dropped and notified. Somebody needs to be deputy administrator in case the adminstrator needs to be dropped.
Don't expect things to work unless money is collected well in advance of the drawing. You want to be sure that all members have ample opportunity to make the payment, and you want time to send any notice that a member is being dropped.
Third, you'll need to detail the rules on ticket purchases and how to establish which tickets are owned by the pool. The best way to do so is to choose your own numbers and list them in the agreement. You'll be playing multiple games, so spell out how they'll be played on the tickets. As an example, 10 games could be played as 2 tickets with 3 games and 1 ticket with 4 games. Nobody can ever make a reasonable case that they played the pool's 3 or 4 sets of numbers by chance. As a practical matter that requires playing the same numbers for a period of time.
Alternate possibilities include specifying where the tickets will be bought, requiring that any tickets bought as personal tickets be bought elsewhere, and that personal tickets are not bought until after pool tickets. Neither of those two options prevents a pool ticket being claimed by a spouse, relative, boyfriend, etc. if there isn't some other way to prove ownership by the pool. Many people are fond of making photocopies, but what happens if the pool administrator doesn't distribute copies before the drawing? Sure, somebody else can buy tickets and make copies, but if the administrator got the tickets but just didn't get around to distributing copies what will you do? FWIW, if the pool then agreed to go out and buy tickets, you may have relinquished your claim to those bought by the administrator if you didn't cover that in the agreement.
FWIW, your state's rules don't really matter in the decison about some players having multiple shares. The pool can take a single check and then distribute the money. Letting somebody play multiple shares will reduce your share, but it increases your chances.