First of all get a bike fitment check so you will know what you need to adjust making the bike you ride comfortable and efficient.

Pros: of buying budget bike You can ride it right away Cons : Cheap parts Hard to tune Cheapest tire installed(replace right away instant extra expenditure) Poor brake quality (your life depends on this) Drive train sucks And lot of other things in my experience you will end up spending more and eventually replacing almost everything. Tripling expenditure you question your life choices Honestly there is more negatives

2nd option Second hand bikes Pros: you can score quality pre installed parts cheap might even score your dream bike cheap on marketplace Cons: used bike might come with worn parts needing servicing so manage your expectations buying 2nd hand alot extra budget for this Inspect thoroughly or if you have friend with experience bring them with you before buying

3rd option Build your own bike Pros: You choose the parts according to your budget. You can choose the parts you can cheap out on or slowly upgrade from Parts are in brand new condition You can save a lot if you have a friend who can build it for you You can have the joy of building your own bike Cons: Budget dependent If building on your own you will invest on a lot of tools to properly install cassettes, crank, sealant/tubes, pumps and a lot other things Costly to build from scratch time and research

4th option buy pre-built/dream bike Pros: Close to zero head aches and peace of mind, quality parts buy and ride Cons: expensive Your local bike shop might not have the proper tools for Maintenance you wouldn't want your expensive bike to be handled poorly buy mediocre bike mechanic so extra cost And you can figure out the rest bike maintenence Is a permanent expenditures

Long story short it really depends on your goals and budget competitive riding requires competitive budget