It's 30 for level 2.
But still, you're going to want Air sooner or later, for battlefield enchants, and those all take gems to cast.
Personally, I do agree that in many cases, the Vampire Count is a superior thug chassis choice for LA Ulm. I just couldn't swallow poor Air access as a primary reasoning for it.
But bear in mind, that the Vampire Count *is* the easy way, and it *is* the expected answer. Especially if you let your opponent know (by using them) that you have Vampires, you might well give him a big surprise when your other choices start making appearances.
Generally, I try to make a point of always diversifying into every path (other than Blood, often too big a bother) during the course of a game. Taking your opponent off guard by introducing weapons that he didn't think you had any access to, can be a priceless advantage. Or in some cases, waiting until your enemy comes at you with his "secret weapon", only to find that with a little effort, you are already prepared to drop a Storm Warriors on your army. Honestly, for the small amount of actual effort required to diversify most paths (a couple of Priests manual searching, they're doing Holy as well anyways), I tend to feel that even just access to a few items you otherwise couldn't get, justifies the expense. Then I let the gems pile up, even at 4-5 a turn, you will have enough to pull off some interesting surprises eventually, and a couple of stray items won't tip off your opponent, as they could have come from victories in combat, or random events.