I would save for a better bike which will come with everything you need and also have a better frame. Do a few upgrades if they improve quality of life, but many useful upgrades require modification of parts (racks often need some brackets cut to fit). Unless you are good there is a good chance you will bend/break something putting it on the new bike. So why not just buy a good complete bike with good components. Sometimes a good seat is a useful upgrade - bikes tend to come with seats that fit males pretty well (because of hip bone differences they don't fit females, seats that fit females are larger and thus more expensive), but a good seat is often a good upgrade for comfort and if you can find one that fits you generally easy to switch.