Unless you're making a fruit beer or are aging a very strong beer for long periods, there is no benefit to using a secondary fermenter - and actually there is potential for harm, namely that you transfer (rack) the beer before it's done fermenting. This removes the beer from much of the yeast that's needed to finish the job, in turn leading to off flavors and aromas and underattenuated beer. Leave the beer in the primary until you verify that it's done - 2 -3 identical hydrometer readings 2 or 3 days apart each - and then package. Good luck.