create table users (
    user_id    varchar(10) primary key,
    ... --standard junk you already have here
    turns_left int default 0,
    last_turn  datetime default getdate()
)

create table misc (
    tag varchar(32) primary key,
    val varchar(128)
)
go
insert misc (tag, val) values ('Turns_Per_Day', '5')
insert misc (tag, val) values ('Max_Turns_Allowed', '15')