Update: Tel1981 has come up with a great solution for the 150 world tour matches.
I have created a spreadsheet to help - https://docs.google.com/file/d/0Bzc18c2hFMLFcXpOTkEzYm9XNUk/...
Here is the list for the 50 gold medals you need to get.
To see what medals you have/need you can access them from the Main Menu - VT3 - Medals.
1 Top Spin Expert: Reach 200 Points For Gold
2 Top Spin Master: Reach 1000 Points For Gold
3 Slice Shot Expert: Reach 200 Points For Gold
4 Slice Shot Master: Reach 1000 Points For Gold
5 Lob Shot Expert: Reach 50 Points For Gold
6 Lob Shot Master: Reach 250 Points For Gold
7 Drop Shot Expert: Reach 50 Points For Gold
8 Drop Shot Master: Reach 250 Points For Gold
9 Clay Court Specialist: Win 20 Matches On Clay For Gold
10 Clay Court Legend: Win 100 Matces On Clay For Gold
11 Grass Court Specialist: Win 20 Matches On Grass For Gold
12 Grass Court Legend: Win 100 Matches On Grass For Gold
13 Artificial Court Specialist:Win 20 Matches On Artificial Courts For Gold
14 Artificial Court Legend: Win 100 Matches On Artificial Courts For Gold
15 Fancy Dresser: Play 10 Fancy Dress Matches For Gold
16 Dress Up Obsessive: Play 50 Matches In Fancy Dress For Gold
17 Friendly Online Specialist: Win 50 Online Friendly Matches For Gold
18 Friendly Online Legend: Win 250 Online Friendly Matches For Gold
19 Ranked Online Specialist: Win 50 Online Ranked Matches For Gold
20 Ranked Online Legend Win 250 Online Ranked Matches For Gold
21 Long Distance Runner: Run 10 KMS For Gold
22 Marathon Runner: Run 50 KMS For Gold
23 Stylish Player: Unlock 20 Playstyles For Gold
24 Highly Versatile: Unlock 20 Advanced Playstyles For Gold
25 Tournament Player: Play 20 Tournaments In Play Mode For Gold
26 Training Gamer: Play 20 Training Games In Play Mode For Gold
27 Exhibitionist: Play 20 Exhibition Matches In Play Mode For Gold
28 Online Touring Specialist: Win 20 Online Tour Events For Gold
29 Online Touring Expert : Win 50 Online Tour Events For Gold
30 Online Touring Legend: Win 150 Online Tour Events For Gold
31 Feared Opponent: Beat All Famous Players For Gold
32 Chameleon: Win As All Famous Players For Gold
33 Early Training Days: Win 6 Different Training Games In World Tour For Gold
34 Later Training Days: Win 8 Different Training Games In World Tour For Gold
35 Career Trainer: Beat Level 8 On 4 Different Training Games In World Tour For Gold
36 Career Gamer: Beat level 8 On 8 Different Training Games In World Tour For Gold
37 Avid Shopper: Purchase 35 Items In The Tennis Store For Gold
38 Big Spender: Purchase 100 Items In The Tennis Store For Gold
39 Right Of Way: Purchase All Of The Court Passes In The Tennis Store For Gold
40 Ambassador: Win 10 Davis Or Fed Cup Matches For Gold
41 National Hero: Win 5 Davis Or Fed Cups For Gold
42 Student Days: Complete All Academy Excecises For Gold
43 Academic Excellence: Complete All The Academy Excercises With Gold medals For Gold Medal.
44 Friendly Nature: Make 10 Friends In World Tour For Gold
45 Nature Compelling Company: Make 25 Friends In World Tour For Gold
46 Perfect Server: Win 50 Points With An Ace For Gold
47 Smash Specialist: Win 20 Points With A Smash Shot For Gold
48 Smash Master: Win 100 Points With A Smash Shot For Gold
49 Clean Sheet Specialist: Win 25 Love Games For Gold
50 Clean Sheet Expert: Win 100 Love Games For Gold
Number 36. Beat 8 games is in fact "Beat 12 games to level 8" but the VT3 screen is wrong. Beat all 12 to level 8 to unlock the medal.
The online matches must be completed and so if your opponent quits out it does not count towards your games won.
Number 25, 26 and 27 can be obtained via quiting out once the match has started. I can confirm this works as this worked for me.
Note 4: Beat all famous female/male players - you do not need to beat the bonus players (henman, king, duke etc.)
Hope this solution helps. I currently have about 27/50 but am slowly knocking each one down.