At what limit can you actually isolate an EP limper?

I play 3/6 and 4/8 live and have been seeing HH here where a MP Hero can isolate a EP limper with a raise. Typical Situation. I have 88 in MP and a loose player limps from EP. I now either need to call and hope for a few more limpers and play for set value, or raise to try to isolate. I have been trying to isolate lately and still get a caller and the blinds to come along. I know have a tough decision on the flop.

At my limits,

1. Should I stop expecting that I can isolate?

2. Should I continue to raise because it builds a pot?

3. At what live limit can i actually isolate with a raise and not a 3 bet?