best 5 rummy apps: understanding the rules and strategiesrummy rules. here are some essential rummy rules to keep in mind: pure sequence: it is mandatory to have at least one pure sequence to make a valid declaration. sequence and sets: apart from the pure sequence, the rest can be sequences or sets. for example, a hand might have a sequence of ace of spades, 2 of spades, and 3 of spades, along with