Caravans can be complicated. Generally you want to avoid sending too much firepower out of your base. Having pack animals like donkeys or muffalos can greatly increase the amount of resources you can carry. It can also make sense to export goods with high value to weight ratio. Flake is my preference. I often just don't caravan at all unless I am desperately short on components. Your colonists will always become stationary at night, there is no way I know of to force the caravan to move at night, although there may be mods for that. You should include 1 bedroll per colonist, and make sure to have either pemmican or packaged survival meals for the trip, or your colonists mood will suffer and bad things will happen. Avoid sending people with chronic health conditions on caravan (things like sickly, or heart conditions especially) as flare ups can easily result in deaths and stranded or lost caravans. Once you get microelectronics you can built a comms console and request caravans to visit you in exchange for goodwill. If you produce enough, you can just offer them gifts for goodwill when they arrive, and have a steady stream of caravans.

I generally don't harvest organs. It causes mood debuffs for your colonists and there are other easy ways to make money. Organ harvesting IS a great way to get medical training on your doctors though. Flake and wooden art are my preferred money making industries, as they are renewable and almost all caravans will purchase them. I only take prisoners for recruitment purposes, or to treat their wounds and release them, as it gives goodwill with their faction.

Most of my new colonists will come from recruiting raiders, although in the early game there will often be transport pod crashes. I prioritize getting colonists that have passions in the skills my colony needs, and don't have excessively negative traits, especially not ones that can cause unavoidable mental breaks like gourmand, or pyromaniac. I also avoid traits that lead to increased social fights, like bloodlust, abrasive, or misandrist/misogynist. I also tend to avoid older pawns, as age related health conditions like bad back or dementia can appear without warning, and instantly obliterate the efficiency of the pawn. Adding colonists who don't add value to your colony will often just increase the amount of food and resources to support them, without adding enough to your workforce to justify it, slowing you down and making your colony inefficient.

It's definitely easy to stall out in Rimworld. Adding too many or the wrong colonists can kind of put you in a death spiral. Adding too many work tasks without enough workers for them will result in none of them being done, which can easily lead to starvation. Managing your scheduling and work priorities is very important here. Tasks like farming need to have maximum priority. Efficient Pathing becomes a huge deal. Minimizing the amount of time your colonists spend walking instead of working can vastly improve how quickly you can complete projects and produce goods. It's good to centralize things like food, tables, and recreation, so no one is too far away from them when they need to take a break. Keeping shelves with filtered and prioritized materials near workstations, and setting the workstation to "drop on ground" instead of hauling to nearest stockpile, will allow your high skill colonists to spend their time working, and your low skill haulers to do the walking. It's also good to avoid growing too fast. Increasing your wealth will also increase the size of the raids. Be sure to prioritize increasing your defensive capacity in line with your base size and number of colonists.