First of all...Welcome to the Cisco Learning Network!
One great article that gave me a lot of light of how to approach my studies of Cisco before starting actively was the following blog, very well written by Gary Pfizer called "6 ways to Build Confidence for the Cisco Certification Challenge". You can check it out here:
Now to your questions:
Should you take the ICND1 100-105 exam and then the ICND's 200-125 exam or should you go directly to the composite CCNA R&S 200-125 exam?
In my humble opinion, it’s good if you go step by step toward your CCNA R&S. Meaning you could start by studying and taking the ICND1 exam to obtain the CCENT certification and you will also be covering half of the material you need to know to obtain the CCNA R&S. Then after you pass your ICND1 exam, you would study and prepare for the ICND2 exam and passing the ICND2 exam you will obtain your CCNA R&S certification. I believe that it’s better to divide and conquer. Meaning it’s much better to learn in small chunks and obtain a better foundation including your CCNA R&S.
My short answer: if you are new to networking, I would advice the two test path and ease yourself into the CCNA R&S track. But if you have been in the field for a lot of years and already know the material and you are just looking into getting certifed then take the one exam route.
Check the following blog that will provide you with good insights abut the CCNA R&S:
Also I am sharing with you the following blog related to the Cisco Certification Testing Experience:
Finally, keep yourself active within the Cisco Learning Network community forums and ask your questions. We are all here to help and learn from each other.
I wish you all the best in your Cisco certification studies. You can do it!!