I've got a Redington Hydrogen 3113. It's the only trout spey I own, and it hasn't disappointed me. It's very light in hand. It can do soft hackle or moderate streamer duty just fine. It has handled trout to 18" for me without a problem.
The shop I ordered it from sold me a #4 305 grain Rio
Trout Spey Head, and a 240 Scandi Short for the rod. Both of these heads will cast, but they're above Redington's respective scandi and skagit grain windows for the Hydrogen 3113. I'm guessing they sent me these assuming I was a rank beginner and needed a heavy head to help me feel the rod load. Unfortunately I did not. If you're interested in this particular rod I suggest you stay within Redington's recommended grain windows, this rod has plenty of feel without going overweight on heads. IMO overweight heads bog this rod down and make any finesse during the cast harder to achieve.
I have since replaced the #4 305 grain Trout Spey Head with a #3 265 grain Rio
Trout Spey integrated line (the scandi-ish one, not the skagit one). I use anything from 7' Trout Versileaders to 10' Light Scandi Versileaders with it. Throws anything from small skaters and wets to #4 heavy wire spey/dee flies. This rod and line allows the use of touch-and- go or sustained anchor casts. If I could only have one line for the rod, this would be it. Very versatile. When used with Versileaders, the line system retains some of the grace of a scandi head while having enough weight in the head to still haul some mail.
Scandi Short 240, with 11'+ mono leaders, works for dry/damp flies and I use it as soon as conditions allow, it is still a little heavy for the scandi grain window however. I plan to replace it with the 210 grain version soon. If your fishing allows it, I suggest you try a full floating scandi. When you find the one that matches your rod and casting stroke, it's pure bliss. If I could fish a full floating scandi head year round (some do, just not me yet) I would.
If you need to fish huge or heavy weighted flies or need to use T-material for depth, choose a skagit head. I have no suggestion for these heads as I don't use them on this rod, but there is plenty of info on these elsewhere here on SP.
Any reel from 6.5oz to 7.5oz empty should balance this rod fine. I have a Pflueger New Medalist 7/8 on mine. It balances fine, and has way more backing capacity that a person should need on a 3wt trout spey.
If you do not choose an integrated line, I would encourage you to steer clear of mono running lines as a beginner. A coated shooting line will still get you reasonable distance with the added benefits of less tangles, and increased ability to mend. As a beginner your priority should be making good contolled casts, distance will come in short order. Chucking huge distance does you no good unless you can maintain control of the swing. My order of preference is integrated line first (no loop to loop connections ticking in the rod guides), coated shooting line second (if you don't mind the loop to loop), and mono last (most distance, but least mend-ability).
If you've got knowledgeable spey shops near you or friends that will let you demo some rods and lines, you should take advantage of the resource (this is something I didn't have ready access to). The only way to know if a given rod and line is going to work for you is to go cast it... preferably with someone experienced there that can help you make the right decisions. Using these resources before buying can save you alot of time, money, and headache.
Hope this helps and good luck!