The fabric attachment system is low-tech, but that seems to be helpful, as it can adapt to seat rails of different widths. One fancier option you might see on more expensive seat bags is a quick-release mount that you install under your saddle. But those have a fixed width, and therefore can fit under seats with only those exact specs. Brooks saddles, for example, are too wide for these mounts.
A wrench that fits the hub nuts:   If your bike has quick release front and rear wheels, you don’t need this, but if you have an internal hub on the back, such as the NuVinci, a wrench that fits is a great idea.  99% of the time, this is a 15mm wrench, but you should check your bike.   A 6 inch adjustable wrench can also work, but it will be heavier, and when using an adjustable wrench, you do need to take more care to not round over the nuts.   A fixed wrench is the best choice.    Some multi-tools have a 15 mm wrench built in, but again, if you have limited hand strength, something with more leverage is a great idea.
Dennis Bailey has been actively involved in bike repair and maintenance for almost two decades. He has worked on bikes on bike tours in the United States, Europe, and Latin America. Keith Gates has been repairing bikes for more than 30 years and provides personalized service as the owner of A-1 Cycling, with locations in Manassas and Herndon, Virginia.
Mini Pump:   This actually goes on the frame of your bike, as it’s a bit too big for most under-seat bags.   Coming soon, we’ll have a review from Bill of his very favorite one, but a good pump is a lifesaver.    Some people instead carry a CO2 inflator, which is faster and easier to use but does require disposable cartridges, and each time you have a flat, you’ll need at least 2 of those cartridges.  There are combined pump/inflator tools that we’ll also talk about soon.
Friction gear systems are a lot simpler to adjust, because the movement of the derailer cable can be modulated as you ride, every time you change the gear- they require less cycle maintenance. Modern index shifting systems are a little more complicated because each ‘click’ must release the exact right amount of cable to allow the derailer to move the correct distance to move the chain from one gear to another. Setting up and adjusting a derailer is not difficult and requires only basic tools, but there is a methodical procedure to follow.