The conjunction 再说 is used to include additional rationale or information to a statement.
再说 can be either placed at the beginning of a sentence or in between two parts of a complex sentence.
When it is placed at the beginning of a sentence:
In addition, we have to take the cost into account
zài shuō, wǒmen bìxū kǎolǜ chéngběn
Besides, I’m not a big fan of social gatherings
zàishuō, wǒ bú tài xǐhuan shèjiāo jùhuì
When the conjunction is placed in the middle of a complex sentence:
I don’t have time. Besides, I’m sick
wǒ méi yǒu kòng, zàishuō, wǒ shēngbìng le
I don’t really like this dress. Besides it is very expensive
wǒ bú tài xǐhuan zhè jiàn qúnzi, zàishuō, tā tài guì le