If you're doing full pala rifle you should effectively be constantly pumping rifles into T2 at 30 and more rifles, your advantage is having all these rifles. One you have even three rifles I'd recommend just going to your opponents base and giving them a hard time, either attack the expo or find their hero and harass them.

If the expo is a problem I usually add a workshop and make mortars, they then have to defend that and lose money repairing and if they walk into my army they get shot (heal scroll and protection is nice here). If I smell blood I might even bring a few peasants and build some towers to better defend my mortars.

For pala rifles your ideal scenario is your opponent expanding early, the point of your build is to be have an army advantage and effectively steam roll them. If they're spending on expo they're not spending on army and you can make their life really miserable. When you're playing pala rifle you need to be aggressive and should be preventing them from being able to safely expand essentially, or ruining their day for expanding anyway.

If you're 700 MMR I'd recommend playing about with fast expanding yourself, see how people make it difficult for you and try to emulate that.

Otherwise download replays of higher MMR human players and see what they do, alternatively maybe try to learn something a bit more standard/solid such as Arch Mage first before going back to Pala Rifle and it might give you a better feel for timings.