Bike improvements. Help needed!

What is your motivation for making changes? Are you planning on racing, or doing some hill climbs? I understand the urge to tweak, but that isn't a very effective route to improving your cycling.

This looks to be a similar spec bike to the walmart/target Schwinn Varsity, which is a functional bike but not really worth upgrading. From an economic standpoint, when you are ready for big component changes, you will find that getting a whole different bike (new or used) will make more sense. The best upgrades to any new cyclist are the "engine". Work on fitness, handling skill and from.

If I were in your position, the only changes I may make to the bike itself would be to add clipless pedals and perhaps the saddle if it were unbearable. Save the money for repairs, your next bike and accessories that you need to consider, such as:

• Helmet
  
• Cycling Shorts and other clothing
  
• Repair Kit: lube, tubes, patches, pumps/inflators, tires, multitool, etc.
  
• Eyewear
  
• Shoes
  
• Cyclecomputer
  
• Bottles and cages
  
• Seat Bag
  
• Lights
  

FYI. 95% of what you will want-or-need to know can be found at www.sheldonbrown.com. Additionally, look at www.parktool.com + YouTube.

Again, depending on your budget, needs, and aesthetic sensibility, I would make changes to the bike in the following order ...

1. CAMPAGNOLO SHIFTERS (<$150 on eBay)
   
2. 'new' SHIMANO REAR DERAILLEUR (<$35 on eBay)
   
3. better hubs and/or new wheels -- depending on rear axle spacing, either Shimano 105 (130mm) or Shimano LX (135mm) -- plus, an 8-speed Shimano/-compatible Cassette will work with 10-speed Campagnolo shifters & most Shimano rear derailleurs
   
4. tyres & tubes as needed
   
5. brake pads, as needed ... possibly, better brake calipers
   
6. crankset & BB are mostly a weight & cosmetic issue
   

The shifters & rear derailleur can migrate to another frame in the future ...

• weight is NOT an issue except for the tyres & tubes, and for a young rider they should not be a great concern, IMO
  

Ditto for the crankset & BB ...

The new -- or, improved with new hubs -- wheels can be used as backups in the future ...

So, nothing is lost if you keep the old parts to put back on the current frame in the future.

BTW. A lot of people will frequently suggest to change the tyres & tubes, first ... they are NOT wrong, but, I think that often presumes a mid-level, or better, bike which already has integrated brake-shifter levers ...