A question for the runners...

Your pace will improve with the more miles you run, so if you want to run farther, run farther. Don't worry about speed for a while. it will come.

I don't think you necessarily have to work on improving your 5K time, but you might want to spend some time just getting used to the 5K distance and feeling very comfortable with it--but not too long (just a week or two) before moving on to increasing your distance.

You should do a combination of both. Look up HIIT on the internet. You should do different combinations of running to develop your slow twitch and fast twitch muscles. I vary my running just like my weight training program. Also I found that my weight lifting routine improved my speed as well as losing all the fat.

I wrote down the various leg exercises as well as other exercises here. You don't really ever want to exercise only one body part unless you get lean enough to see imbalances, or else you actually create imbalances in your body. http://www.myfitnesspal.com/topics/show/746754-how-to-get-abs-with-pics

The routine I do consists of weight lifting first and cardio second, but I still do cardio (mainly running). I change up everything all the time. My running is sometimes long easy runs, sometimes HIIT, sometimes shorter medium pace runs. My weight routine changes each day, each week, Circuits, Intermittent Super Sets, Fibonacci Pyramids, X-sets, Progress Venus Pyramids, and some splits, constantly changing it up, everything a variety of Strength, Hypertrophy, and Endurance.

Legs; In addition to Dealdlift's, Stiff Leg Dead Lifts, Sumo Dead Lifts and Squats I do Bulgarian Split Squats, Lunges, Reverse lunges, Curtsey lunges, Step Ups, Crossover Bench Step Ups, One legged Deadlifts (T-Bend), Lunge Matrix, Bowler Squat, One Legged Get Ups, Bower Squat and calf Raise, Bowler Squat + Stiff Leg Deadlift, Curtsey Lunge + Dumbbell Squat, T-Bend + Y-Squat, Reverse Lunge & Step Up, Curtsey Lunge + Step Up, Y-squat, Narrow Stance Squat

For upper body I do Standing Shoulder Press, Standing Dumbell Curls, Lying Tricep extension, Pullovers, Bent Barbell Row, Standing lateral Raise, Standing front Raise, Curl and Press, Shoulder Press + Curl, Dips, Lying Tricep Extensions + Flyes, Venus Raise (a type of snatch), Bent Row + Standing Lateral Raise, Pullovers, Pushup + Dips, Standing Dumbbell curls + Overhead Tricep Extension, Bent Lateral Raise + Pullovers, One Arm Dumbbell row, Flyes + Pushups, Seated Curl & Tate Press, Seated Curls + Overhead Tricep Extension, Pushups, Pullovers + Dips, Bent Barbell Row, Lateral Raise + Full Front Raise, Venus Raise + Dips, Standing Dumbbell curls + Lying Tricep Extension, Upright Row + Dips, Bent Barbell Row, Flat bench Press, Incline Bench Press, Bent Row Narrow, Bent Row + Kickback,

Then some upper and lower combos; Squat and Front Raise, Step Up & Press, Step Up + Standing Shoulder Press, Squat & Press, Squat & Swing, Curtsy Lunge + Standing Shoulder Pres, T-Bend & Row, Pike Front Rais + Curtsey Lunge, Flat Bench Press + Step Up.

Core: Bar Bell Rollouts (you can start out with Stability Ball Roll Outs), Swiss Ball Pikes (you can start out with Stability Ball Curl Ups), and planks. As you advance Swiss Ball Pike and pushup.

I probably forgot some but you get the idea.

Your pace will improve with the more miles you run, so if you want to run farther, run farther. Don't worry about speed for a while. it will come.

+1

Honestly, do which ever you want. I stayed around running 3-4 miles before my first 5k run for a few months (I didn't do couch to 5k... I just started running, hahaha). I did that because that's what I felt like doing. After my first 5k, I realized I loved racing, so I decided to do a 10k, and right after my 10k, I decided I wanted to do a half marathon. I'm a milage junky, so the thrill of running further was exciting to me.

After my half, I'll probably work on speed, because that's what I feel like doing right now. There's no right or wrong way, just do whatever you want.