In your case, performance (ie how fast can I go) is secondary... exercise and general health are primary.
Therefore, don't ride so hard that the soreness keeps you off the next day.
And the next day, don't let the soreness keep you off, rather reduce your exertion level and ride regardless.
Soon, as your fitness improves, you will want to ride harder and faster, both because you can, but also because the faster you go, the more calories you burn per mile. But don't ever let that overshadow the plain enjoyment of being outside, being mobile, being active... just riding.