In my opinion, there are only few games to bet on : Troicki-Goffin, Gasquet-Paire and Cilic-Simon. For all other matches, I cannot really imagine the underdog winning, but the odds are to low to pick the favourite.
Troicki - Goffin : if we look at this season records, Troicki is 14W/7L winning Sydney tournament but his only significant win is Dimitrov. He defeated Johnson but this was the first week of January, all the other wins are people outside Top30. Goffin's records : 15W/5L but wins against Wawrinka, Cilic last week, Thiem, Coric. He made me a really good impression last week and I think he will win this one.
Gasquet-Paire : Paire is the guy you don't want to bet on because he can play great tennis... or lose against anyone. Gasquet plays good, I think he will win but the odds are too low to bet on him. If Paire is in a good day, he can definitely win, it looks too risky to me but someone may take it.
Cilic - Simon : Simon leads 4-1, everytime it went to the decider set. Simon hasn't played really well so far, but I think he can really upset Cilic with his game style.
For my bets, I put 10$ on Goffin, and 3$ on Simon.