I dislike this topic for one reason: A lot of people are quick in regards to giving him their opinions on how he should reach his goal, but nobody is really giving their opinions on how he could do better with the character that he likes.
Down Throw -> Up B is great for piling on damage (12%) whenever the opponent has too much damage that you can't follow up with an Up Air. You can also mix up your options after a down throw by turning around before jumping, which would cause Dr. Mario's Up Air to send the opponent behind him, which makes it possible to follow up with a Back Air. You can also use Down B instead, which isn't a combo, but it is good for catching airdodges and the last hit has a surprising amount of knockback at the end of it which is useful for sending the opponent offstage. Down B is also surprisingly good at edgeguarding too, especially against opponents who try to recover high, but it takes practice to master as you have to be really careful off of the stage with Doc, and burning your Down B means that you are burning his recovery. So use it wisely. Otherwise Back Air is the to-go option for edgeguarding because of its speed, damage, and knockback.
Doc's Down Tilt, like Mario's, is good for frame traps at lower percentages. So you could do Down Tilt -> Grab when you feel as though the opponent won't be able to react to it. At mid percents, Down Tilt -> Up Tilt is a combo that puts your opponent into the air (for aerial followups), though there is a better combo which I feel as though is overlooked by people. Down Tilt -> Up B is a true combo at low-mid percents which, when you sweetspot the Up B, does 19-21% damage. It is also safe, because you can turn the Up B around during the hitstun of the attack and fly in the opposite direction. It does reset the match to neutral however, but free damage is free damage I say. Also, Doc (like Mario) has the 2nd fastest Down Smash in the game, which is very useful for sending the opponent offstage and/or KOing them at high percents. And his Up Smash, while only being the 5th fastest Up Smash, makes Dr. Mario's head invincible (also like Mario), making it great as an anti-air.
That's pretty much all I know though, as I don't main Doc (I main Mario). But hopefully, this helps you out @
shadowrohas. Always remember to keep practicing, learning, experimenting, and most importantly adapting. There's probably a lot of things about Doc I don't even know about, that you could end up learning. Be sure to check out the Doctor Mario section on the character boards if you wish to learn more:
http://smashboards.com/forums/dr-mario.502/
Lastly, I highly recommend that you try out the entire roster of characters, and see which other characters could also suit you. What I did was that I went through all 48 characters (51 if you count Miis), and gave them a rating of 1 to 5 based upon how much I liked them. You don't have to do the same thing I did, but who knows? You may end up finding someone that you like that you might've not even considered playing before. Plus, if you plan on playing competitively, it is always a good thing to have multiple characters at your disposal instead of just one, as different characters do better or worse in certain matchups in comparison to other characters. And always be sure to check the character boards, competitive discussion board, and youtube/etc for tips and tricks at how to improve at Smash Bros:
http://smashboards.com/forums/wii-u-3ds-character-discussion.291/
http://smashboards.com/forums/wii-u-3ds-competitive-discussion.509/ (well you already found out how to get here lol)
Good luck!
