Hi amico, 30 minutes is good, because it filters to you the bit and pieces.......
You have to consider that 20% of the time the high/low of the day is made in the first few hours, it is more common for market to revese the opening than continue, if market pushes price up and at a level makes an healthy reversal on the 30 minutes, you would be wise to place a sell stop order below that reversal bar, it could be the high of the day.......
Once you gain confidence in this particular stile on the 30m, then you will start to take trades also on a smaller time frame or viceversa, I mean.... in the case of today EU trade I entered after the 15 bar because the 5 bar did not convince me in his reversal, the 15 did convince me considering the fact the GU was already going down strong...as a correlation. If the 15 was not convincing I would probably look at the 30m TF next....normally if the bucks stops there (30m bar) it would print a nice pin bar.