Hi Duke of Gloucester,
You've got the basics of what you need. You'll also need control vinyl (if using records) or the control tone (on a USB or on a CD) if using CDJs/Media players as well as any mixer.
Here's a step by step guide to setting up the SL3, which is similar to the SL2 except it has 3 channels instead of 2:
support.serato.com
Unfortunately, the SL1 is discontinued and does not work with Serato DJ Pro, only Scratch Live which is also not supported on newer operating systems - so the DVS expansion pack will not allow you to use an SL1 with DJ Pro.
FYI - you're currently posting in the Serato Studio section of the forum (this is our beatmaking product
serato.com) - in the future please post DJ questions in the DJ section of the forum:
serato.com :)
Thanks!