As you deduced, a real capcitor has a frequency dependent and complex capacitance. To determine how you can measure it with limited instrument means, you should get a rough idea of the expectable values. A capacitor datasheet is the right place to look for.
You'll notice that the real impedance component, which can be either represented by a series or a parallel resistor in the equivalent cicrcuit, will be usually specified as loss factor or tan D value. You'll surely be able to convert it into an equivalent series or parallel resistor.
You should be also aware of the existence of a series inductance and a respective series resonance frequency. If you are measuring capacitors at 20 or 30 MHz, you might even catch the resonance.
Before modern LCR meters were developed, bridge circuits had been used for component measurements, e.g a Wien bridge. They can be still used today.