Sword and Silver Tongue, Consultants
Humanity does as it wills…
The year is 2960, and this timeline will radically diverge for the worse from the official Battletech storyline. Think of a mix between Firefly (sci-fi frontier planets mixed with big cities), Snow Crash (cyberpunk dystopia), and Mad Max (post-apocalyptic). Mostly 22nd and late 21st century technology, but a spread from early 20th century to 28th century is possible. Mostly realistic and slightly cinematic (larger than life action hero stuff).
Faster-than-light (FTL) travel developed in the early 2100s, and a dozen planets were first colonized in 2108-2235. First wave planets were colonized largely as international projects. Second wave (2150-2800) was funded mostly by corporate endeavors. Third wave (loosely 2300-2900) was comprised of dissidents and outcasts, societal rejects and extremists — either exiled by their betters or fleeing oppression and persecution. There are a total roughly 240 such core planets, averaging 350 million to 4 billion in population, with known extremes from 90 million to 17 billion.
All told, the core planets are spread across roughly 3000 light years (the Inner Sphere), but the total sphere of human colonization spans 8,000+ light years when including the farthest known extents of the Deep Periphery. Planets in the Periphery may have hundreds of thousands to a few million inhabitants, with many lost or failed colonies now dead or only small communities of a few thousands to tens of thousands struggling at a subsistence level.
These are all ballpark numbers. No one really knows how far humanity has reached, or how many people are alive now. Peak population at the height of the Star League was about 1.5 trillion, now estimated to be only 400 billion. Humanity is scattered across hundreds of planets, in a portion of the galaxy that includes millions of stars — plenty of uncharted / inhospitable territory. Due to the immense start-up costs of founding new colonies, humanity has scattered like dewdrops on a fragile, immense skein of spiderwebs on those planets colonizable with a minimum of adjustment or terraforming.
Interstellar starships called jumpships can cover 50-150 light years. Interstellar jumps near-instantaneously fold space locally. Due to fuel / jump recharge limitations (10-20 days per jump), it still takes 2 to 15 years to traverse the entire Deep Periphery, or 10 months to 5.7 years for just the Inner Sphere. Jumpships are too fragile and unwieldy to risk in the shock of atmospheric reentry. Smaller dropship craft serve as mules, interfacing between jumpships and planetary/orbital facilities.
FTL communications (other than sending a ship) developed a bit later, and now have roughly twice the reach of a jumpship. About 30 remaining planets have still-functional Comstar class A hyperpulse generator (HPG) stations, comprising the Prime Circuit.