--expiry|-E Upper bound on how many seconds after getting work we consider a share from it stale (default: 120)
--scan-time|-s Upper bound on time spent scanning current work, in seconds (default: 60)
--queue|-Q Minimum number of work items to have queued (0 - 10) (default: 1)
What atp1916 suggested works best for R9 290, other cards might require different values.
It has much more to do with the coin you are mining, not what cards you have. 10, 5, 0 are good values for a multi-pool. You can go down to 2, 1, 0, but there isn't likely to be much change. (some people use 1, 1, 0, but I find this results in too much work expiring).
Queue 0 is the most important. Expiry is fairly irrelevant.