Not all small parties that I see on the Wikipedia list even run in the elections? That's weird, makes it look like they aren't even trying. I think they should attend symbolic. Like "hey we are here. We exist" Just being on the Ballot also makes a difference.
But yes, as you say, building up local support should be the first step. My Party lost the seat in the European Parliament, but we actually had many local Elections at the same time, and local we actually won new seats in some City Councils. I hope the people that got that seat will keep up good work and also speak about it, because most people don't even notice anything that happens in their own Councils. That way, we maybe get more votes from people out of that city in bigger elections.
Einer muss es ja tun