The United States started taking a national census every 10 years starting in 1790. Unfortunately, Virginia records do not exist anymore for 1790 or 1800.
Also all US census reports from 1890 were destroyed. Wars and fires are to blame. It is also worth noting that most names back in the early 1800's were spelled phonetically on census and other legal documents.
You will see Gillespie spelled in the following ways: Gillespie, Gillaspie, Gillispie, Gallaspie, Gallaspy, Glaspy, Glasby, Gillaspee and other random variations.