Before getting any premade cue, you should hit a few balls with different cues, tips, and shafts... try different weights, etc. It would suck to spend a lot of money on a cue and feel like it isn't right for you after the first week or two. Make some buddies at the pool hall and borrow some cues for a while, see if you like the feel of any of them.
There really isn't a single best weight or length, it depends on how your body is built and your playing style. What works well for someone else might feel really awkward for you.
If you want just an average figure to start with, 19 oz is the most popular weight, 57" (or was it 58"?) is the most common length.
In the past 10ish years the most major advance in cues has been low-deflection shafts. These shafts generally have been hollowed out and made for lightness and flexibility, so that the shaft bends away a little more when you hit the side of the cue ball. That basically means when applying sidespin, instead of the stick being rigid and deflecting the ball a bit sideways, the stick 'gives' and the ball moves in a straighter line.
The end result is if you're applying lots of english, you don't have to adjust your line of aim as much as you're used to. You can almost aim a heavy spin shot the same way you'd aim a shot with no spin.
I think a majority of players have decided they like this trend, but a few still grumble that you don't need no fancy special shaft. A few will even tell you it's all marketing BS, but if you spend ten minutes hitting with one, you'll find that's obviously not true.
If you decide you want to give these shafts a whirl, the 2 most popular brands of LD shaft are Predator and OB. A Predator Z2 or and OB2 would be the typical shafts most people go for when they get a low deflection shaft.
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Jump cue technology has also come a long way, they're making the tips on jump cues (and break cues) very very hard, similar to the pool balls themselves. Today's light jump cues with rock-hard tips make jumping incredibly easy.