There is a rigging table on the main menu if you mouse over Info, Articles of Interest and click on J/30 Rigging Information. You can get good products from the major suppliers. I like the Samson and New England Ropes products. The halyards can be a high tech core that is low stretch with a good quality woven cover. A lower priced but adequate line for halyard is New England Ropes Sta-Set X
. It is a parallel core line that is stiffer than lines with a high tech core such as Spectra or Dyneema and much less expensive. It is difficult to splice unless you have some experience, so better to have a rigger slice on the shackle. For club racing and cruising it is fine.
Don't skimp on the jib sheets and if you have self tailing winches, make sure the diameter meets the requirements of the winch tailer. Jib sheets get a lot of use and you want a line that is easy on the hands, doesn't slip, doesn't hockle (twists and loops) or doesn't chafe. I like Samsom MLX
because it has a tighter weave on the cover and wears better. You can go with stripped halyards for performance to reduce weight aloft, but you will sacrifice line life. If you do mostly cruising and club racing, I wouldn't strip the halyards.
Spin sheets on the other hand will greatly benefit from being stripped. In light air you don't want the weight pulling the clew down. Some think the high tech cores are too slick for a bowline. An easy way around that is to put and eye splice in the end and use soft shackles to attach to the spinnaker. I have used New England Ropes Endura Braid
and Samson Warpspeed
The roller furling doesn't need to be high tech (and isn't stock on the J/30 but many have it). New England Ropes Sta-Set
is good for that.