AND(test1, test2, ...) is TRUE only when every test is TRUE; OR(test1, test2, ...) is TRUE when at least one is. Put them inside IF to make one decision from several facts: =IF(AND(B2="Gold", D2>=1000), "Invite", ""). NOT(test) flips TRUE and FALSE.
IFS(test1, value1, test2, value2, ...) checks the tests in order and returns the value for the first TRUE one. Order matters: put the strictest band first, IFS(D2>=1500, "Platinum", D2>=500, "Gold", ...), or every big spender stops at the first, looser test.
IFS has no "otherwise". If no test is TRUE, it returns #N/A ("No match."). Add a last pair with TRUE as the test to catch everything else: ..., TRUE, "Basic").
=IF(AND(B2="Gold", D2>=1000), "Invite", "")
=IFS(D2>=1500, "Platinum", D2>=500, "Gold", TRUE, "Basic")
Invite big-spending Gold members; a spend band with a catch-all.