defending

have starbases and build your defending ships right before you run out of dp.. (like when you have about an hour or so left

One thing most people do, especially on RT but also on the slower servers is to use multiple windows. I usually have a minimum of 12 windows open while fighting. I have one window on the attack screen. I have another window with my Manage Fleet screen and 1 window for each of the ships I plan to build. I type the number of each ship I want to build in each of the 10 windows. Then I go from window to window clicking the build button in each window. This builds you 10 stacks in a matter of a few seconds. In RT I try to use 10-15 turns total. Then I refresh each window for each ship I want to build more of as my turns regenerate. I refresh the attack screen constantly keeping an eye out for anyone within attack range... If I see someone above me that might attack me, I use several turns building bigger PR ships so I leap frog them on the rankings so they can`t attack me.

The individual ships you choose to use or the number of different ships you use in your stacks is up to you. Since you`re a smaller empire that doesn`t have much cash you might want to stick to 4-5 stacks instead of 10, but that`s your decision. You`ll have to work that out to see what works best for you.

Personally, I don`t use starbases very often. They might seem like they could defend you all on their own, but in practice that`s not always the case.

well starbases can be easily defeated , but so can offencive ships , you can also build scouts in dp so if you want , build 2 stacks of starbase , 1 of each of your scouts , then start building your stack , then its up to you if you want to keep the starbases , you do not need to use all your turns on just 1 stack , you can use a few turns per stack then build upon each one step by step.

but every ship can be beaten so saying use this and use that would be incorect

there is no 1 stack that can garuntee you a victory, even on the defensive

in fact there is no combinations of ships that can give you more than a 90% chance of winning against anybody(rough estimates there)

so that means, you need to learn how to stack, and build ships faster. Stacking is a skill that takes a long time to develop, just get to know ship stats and what they mean, and fight battles and see what works with what, against what enemy ships etc etc.
building ships faster... well, just know what you want to build, or have an idea, build some, but make sure you have turns left over so you can continue building, so you dont sit at one power for a long amount of time. when you do that, the longer you sit increases the liklihood you will be attacked, so keep on the move, and dont spend too many turns at once