The first few orders you could probably do back to back but soon the experience gap between levels will widen where the story orders will no longer appear until you acquire additional xp from other sources. When the game first came out people could and did look through the various game files and found text describing all the story orders but not all of them were released and available (reasons were never clearly given but some of the text implied the need of additional content not in the game at the time). Thirdly, the story must also be released (not at all obvious). Even though the level is what unlocks the order in reality to complete them you need to actually buy certain skills, specifically the garage expansions to unlock the paint booth. Secondly, each has a specific level you must be to unlock them (not so obvious but fairly standard in most games). And need to be completed in this order before the next one will unlock. First, the story orders are unlocked in a specific order (fairly obvious and standard for most games).
