I tried a constant lighting setup and was disappointed, granted it was cheap.
I agree with Brooke and i don't think you'll be disappointed in the Yongnuo setup and price. I knew nothing about off camera lighting and started with three YN560s and a YN560TX controller. The Nikon version of the controller works with Pentax. I've since added 4 more YN560s and another controller. The YN560 IV speedlight has a controller built in, so you can use a YN560IV on your camera as a controller if you do not want to purchase the YN560TX dedicated controller. I prefer the dedicated controller as yet I have not shot with on camera flash. Two controllers allow for two different camera/lens setup during events. I've done a few dances where they wanted portraits with a backdrop setup. I offered to also take some pictures of the dance, mostly because i wanted the experience with lighting setup. I set up three or four of these in the dance area and one camera/lens/controller for the dance and the other camera/lens/controller for the portraits. During breaks in the dance folks would line up for portraits and it was good to be setup for that since the breaks were short and folks didn't have to wait. The folks i did the pictures for were very happy with the combination of portraits and candid dance shots and have asked me back for more. For me the Yongnuo setup is a gem, but just my opinion.
I mainly went with the Yongnuos because of price and I wasn't sure if off camera lighting would be my cup of tea. I've since learned there is some much flexibility and things you can do using off camera lighting with manual speedlights -- it definitely has me hooked. It just adds another series of things to life I want to try out in all the spare time i can't seem to find.
Make make sure and get a good set of high capacity rechargeables and good chargers and possibly a battery pack for your flashes -- that is another topic in itself. I did the amazon high capacities AA's as the price point is good. Altura Rapid Fire Pro battery packs (no longer available on Amazon), but similar to Neewer External Flash Battery Pack CP-E4. For charger i did the OPUS BT-C700. In the end though I think it may have been better to have gone with something like the Godox PB960. The initial price for one Godox battery pack would hurt, but if i add up the cost I've spent in high capacity AA's and the battery packs i think i could have gotten a few of the Godox PB960's and had plenty of power to supply multiple flashes on one light stand. just something to consider.
One good thing is that you don't have to worry with how quickly your shots are done since your subjects are inanimate, or at least I think so, so you have time to experiment and learn what setups work best.
{edited to clarify link}
Maybe you are beyond this, but thought i would throw a link to this resource in --
strobist.blogspot.org
I am no off camera flash expert for sure and i frequently look back to this resource to refresh myself. I like his style of presenting the material and he gives plenty of examples. I'm pretty sure there are some examples of product lighting. I know he has a page with a ton of DIY links, and pretty sure there is one for building a light tent. If anything looking through his stuff gives some good ideas of things to try out.
good luck!