hello.

Of course, to conserve as much ports pin as possible you
should use serial ADC.
You will need only DO, DI, SAR, CS, SE, CLK lines - summary 6 lines.

But what you need to convert???
Is it a constant value or very fast changing value.

Setup CLK to create ticking use timer or any pulling method.

The procedure of reading ADC is simple just:
1. Select a chip CS = 1,
2. Set up on DI number of input to conversion 5 bits;
3. Set SE to 0 start conversion;
3. Wait for line SAR Status to 0 end convertion(convertion time)
4. Read 8 bit by bit DO.
there is a datasheet.

datesheet

Do you really need a 8 input ADC???