First, know that the goal is to try to get your adjacency bonus up to +3 for the Rationalism card.
Here are some options:
- use the Government Plaza and the City Center to bump a Campus up to +2. The other Districts you put next to the Plaza (like, say, more Campuses) will bump it up to +3.
- Use Jungles and other Districts
- Don't forget Reefs give you a major adjacency now.
Even when I am going for a Science Victory, I may not build a Campus in every city. Play the map: don't try to force a Campus into every city, build the District that best fits what the city can do. Coastal cities are good for boosting trade (just don't overbuild on the coast, I still think inland cities have an edge). Flat tile cities are a bit weak, but they are pretty good locations for Industrial Zones and Commercial Hubs.
That leads to another conclusion: if you don't have a direct Civ bonus to Campus adjacencies, your ability to have a Science Victory can be determined by the map you get. Civs like Australia, Maya or Korea are basically guaranteed to get as many strong Campuses as they like. That's one of the reasons they are so strong for a Science Victory. If you are playing a Civ like Rome, and you don't get a lot of mountains, then you should probably go for a Domination Victory. That's what Rome does best.