It's hard to say exactly how many baffles I'd use, because this depends on the sump design. Here are a few general rules as to number and placement.
You use baffles for two reasons. You want a bubble trap, or you want a different level of water in one part of the sump.
You usually want to install baffles in pairs spaced far enough apart so you can get whatever tool you plan to use in there.
Flow can be under or over a baffle. For a bubble trap you usually want the flow under one and over the other.
The return area need to be larger than you think. It's got to be able to hold enough water so the sump will not run dry. The entire sump needs to be able to contain all the live water in the system.