Protecting Your Economy
Defending your income, planets and labs is important. While the eco player is alive and kicking, the team is usually alive and kicking. Do not hesitate to spend money to protect yourself if you feel the need to do so. Starbases are usually the best bet because they not only have the highest defensive potential, but they also can keep your planets under control regardless of bombardment. You can also get trade upgrades on starbases, which provide a good income (huge for TEC). As Advent, you can get a very powerful culture on starbases, as well as allegiance improvement upgrades.
Cannons (Gauss, Missile Platforms, Beam Platforms) are also a good bet early on. 5 cannons will kill a mid-level marza faster than it can deny a 2500-health asteroid even with Raze Planet active. They will also easily keep 20-25 light frigates off you if you build the cannons really close to each other.
Cannons are not good vs. corvettes. TEC have hangar defenses with flak upgrades. One hangar will easily keep 40 corvettes off you, Vasari have Orkuluses which can move and do huge damage to corvettes. Advent are the biggest victim of possible corvette invasions.
If you feel that you might get attacked, do not rush to build counter fleets. Using 20-30 LF or 40 corvettes to bypass you is not usually a good idea, as you can then build your own corvette/lrm fleet and the enemy will not be able to run to their worlds or reinforce the attacked forces. So in most cases, when the enemy sees a starbase made by eco player on choke, he will not risk bypassing.
As Vasari, you might want to make use of Phase Jump Inhibitors, which are available early.