they are the msot troublesome but they are also the most expensive components (imo) to purchase. Just get what you need (i.e. i5 or i7, k or non-k version) and the mobo get something that suit your wants (i.e. size of case, ITX, ATX, SFF, single GPU, dual GPU, small GPU, fat GPU).
There are alot of customizations, so you need to know what the pc is used for, or what you want it to be. I cant tell u that ATX board is the best if all you want to build is a ITX case, and be placed on your computer table, or telling you gtx1080 FE is the best, but all you can afford is a $299 1060 or $250 960. Too many factors for us to advise, but you need to understand your own limitations (i.e. money/budget, space constraints, usage constraints)
if your budget for PC is below $1k, or you do not wish to increase your budget, its better to not perform upgrades and get components that are most durable (e.g. gigabyte) and with longest warranty (e.g. zotac). Note i am not promoter for any of these brands. Even if your budget is $2k, the above rules apply. Because by upgrading ur PC, it will cost anywhere between $200-$1k to change components and it may not suit everyone.