When I was a kid I used to have an old worn out deck that I kept in the garage that I called my “motorcycle deck”. The name didn't come about because there were pictures of motorcycles on the cards or anything like that, but rather because I used to take a card every once in a while and slip it in the spokes of my bicycle and when the tires turned it sounded like an actual motorcycle. To my recollection that was the first modification that I ever made to my bike, but I have made a few others since then, and all of them played a pretty vital role. If you would like to know a few of the more important ones, then you came to the right place.
If you have a BMX, one of the most significant changes that you can make is to get some better BMX handlebar grips. Changing the BMX handle bar grips that your bike already came with is a good idea for two reasons. Firstly, there are plenty of different types that you can choose from that come in a variety of different materials, colours, and which can allow you to take a better grip than the standard ones that most bikes come with. And secondly, seeing as how the BMX bike is perfect for a more energetic riding stile, it is almost certain that a lot of riders will wear out their grips much faster than they would on any other sort of bike.
Next up on the list there are the pedals. Much like the handlebar grips, these will get worn out much more quickly after a shorter time than most other components simply because of the function they serve. However, this particular part of the bike suffers even more punishment because of how much force is applied to them on a regular basis. You can also pick out a set of pedals that are not only more durable than the standard one, but that will also lead to your feet slipping less even in more unfavourable conditions when the roads are wet or covered in mud.
And finally, there is the bike chain and the reasons why you really need to keep at least one spare around. While there are a lot of benefits to switching out your chain, getting a spare that you can use in case anything happens to the original is actually a better idea. The best option is probably to get a new and better chain that you will use and keep the old one as the spare. This will undoubtedly come in handy since while the grips and pedals were important components, you can still ride without them, while the same can't be said about the chain.