How to program the ADC10 on an MSP430G2553?
Your settings look correct.  I get the feeling you're unsure about clocking, though.

In your sampling sequence, keep ADC10ON set to 0 until the rest of the registers are configured.  Then, when you are waiting to sample, don't wait a specific number of cycles.  Instead, poll ADC10BUSY until it is 0.

The 64 clocks referenced in the sample-and-hold time setting ADC10SHTx are not CPU (MCLK) clocks; they are clocks relative to whatever clock source you select with the ADC10SSELx setting, divided by the ADC10DIVx value.

With your current settings your ADC is running from the ADC10OSC (ADC's internal oscillator) which runs at roughly 5 MHz, and you're dividing that clock by 1.  Your sample time is set to 64 clocks, or 12.8 µs.  You could multiply this sample time by 2, 4, or 8 by dividing the clock by the same value.

What your sample time needs to be depends on your hardware -- specifically, how long it would take for your voltage source to fill a particular capacitor.  If you don't wait long enough, you'll still get a reading, but it will be incorrect.  The MSP430 Family User's Guide has more detail.  However, the "just make it go; I have all the time in the world" setting would be to use the ACLK source (12kHz assuming ACLK is sourced internally from the VLO) divided by 8 (=1.5kHz) with 64-clock samples for a 42ms sample time.  It will actually take 77 clocks as you've calculated above, so the reading will take roughly 51ms to complete.  This is really slow and gross overkill, but it's not a bad starting point to tune from.