Sometimes it doesn't really matter what clans you use or how their bonuses go together as just... picking 8 good cards. I mean if it's an Ongh week and you decide to use Jungo and Uppers... does they really synergize any particular way? Not really. But it kicks butt!
That's the beauty of split decks and why it's so fun. You can use almost anything.
The only basic rule I can think of is that you don't want to use two clans with the same bonus. Like don't use Sentinel with Junkz because you might as well be going mono, except that sometimes you'll get a 3/1. I wouldn't use Sentinel and Sakrohm either cuz that's also pretty much the same unless you're going against Montana.
There ARE however SOME basic things that 'go well together,' but they don't always work as well as you think. Vortex with Frozn. Freaks and Pussycats. Huracan with Jungo.
The way -I- play... I always like to have 1 attack manipulation clan and then 1... something else. One thing to cover low pill rounds and 1 thing to cover high pill rounds. Ulu Watu and Montana for for example. Uppers and Roots. Something where, maybe you have a defeat card, but they can't hold because you MIGHT use another card.
Freaks+jungo and freaks+sak are classic combos (poison + life gain)
Vortex + a big gaping clan like jungo, frozn, FPC, etc
Roots + high powered clan (ulu watu, bangers, frozn, FPC)
Piranas - opponent pills half + high attack manip clan (junkz, sentinals, etc)
uppers + nightmare i dunno it just works
It's hard to score consistently in ELO without some form of damage reduction. I wouldn't have more than 2 in your deck though because you will occasionally only draw your 'loser' cards and that makes for a rough match. The problem with damage reduction cards is that they're pretty obvious so it's best to use them on reprisal rounds. Veenyle Cr for example... Artus... great cards but if you lead out with them the opponent pretty much knows what they have to do.
Spiaghi is a good card because you can very often force an opponent to use 2 extra pills to beat him. Along those same lines cards like Marina/Maurice/Diana are good cards because you can mid-pill with them, possibly do some damage, or at least not take much. Almost every game has a "50/50", even if it's in the first round. Forks are great because they eliminate the eerie feeling of 'should I use 0 pills or should I use 7'