Heres the general theme I have in my head, this is mostly sequential
carbs from meal -> glycogen manufacture/storage to 5% liver weight, insulin release, blood sugar stability in healthy individual -> blood sugar begins to fall with cell activity, "glucose is gone" (glucagon) release, glycogen breakdown from liver (and a few other niches) released to blood and holds blood sugar steady -> liver begins to run out of glycogen and cells still want glucose, sugar supplies depleting -> gluconeogenesis activity increases to meet the demand for ATP over time.
Now what you also have to remember is that gluconeogenesis is probably occurring even in the presence of blood sugar, to some small degree. We know that resting muscle fiber is always metabolizing fatty acids to preserve glycogen stores for heavy lifting (fast twitch fibers keep glycogen on hand). We also know there is a constant turnover of fatty acids into and out of the blood stream regardless of the state of blood sugar.
I like to think of them as separate systems, in a way they all occur simultaneously; i.e. there is always some fatty acid and protein breakdown to create ATP even when glucose is highly available. I must imagine that the body will preferentially use (burn) whatever source is in highest supply i.e. if you eat ALOT of protein and very little carbs I tend to feel that de-amination will accelerate to make use of all the excess free amino acids. Also remember that muscle cells can release amino acids to maintain free amino concentrations in the blood stream to supply energy when glucose is gone to cells that preferentially use glucose. The real roadblock to learning anything specific (or a specific order) is that each individual cell type is preferentially using (burning) a particular set of substrates in varying concentrations, so a generic question like "when glucose is gone what happens" is impossible to answer without knowing with respect to what cells are responding. Another issue is the machinery on hand to deal with the demand will vary, for instance somebody who has NOT been eating carbs for a week or month would have more mitochondrial activity and gluconeogenesis machinery on hand to deal with fatty acid handling/transport/breakdown. Where someone who has never been without carbs, and suddenly stops eating carbs, will likely suffer a delay (and fatigue) while the internal cellular mechanisms signal for a higher transcriptional activity of machinery used to produce ATP without glucose.
