I've posted this in the thread about approaches. I'll post it here too:
Honestly, as a new player, you'll notice an immediate increase in success if you stop seeing approaching as 'attacking', and start seeing approaching as 'staying in control'.
You won't be too good at starting crazy combo/string chains, so keep it simple at first and master the basics. And I mean MASTER them. The basics are the most useful set of skills to master. Let me explain.
I've been trying different characters, finding my main. Per usual for me and Smash Bros. And while each character may have a good fair shorthop approach, or dair approach, or dash attack approach, or whatever - they all have the ability to be patient, dodge the enemy, and land a grab or jab combo. THAT is the bread and butter of Smash 4, especially for players new to competitive smash.
A lot of us aren't at SSB64/Melee/P:M level where doing a great attack approach out of nowhere can actually lead somewhere for us, combo-wise. Sure, you may land that fair or ftilt, but then what? Do you know the options your enemy will have, and do you know the optimal way to follow up? And that's if you even land your attack - you may not. And what happens then? Likely, you start rolling around, or jumping, or spot dodging, or sending out random smashes because you hope the enemy makes a mistake.
Take it slow and boil your character down to its rock-paper-scissors essence when you're trying to learn and improve at Smash in general -- shield, grab, and/or punish. Do one of those.
Rolling is good, but you'd be surprised at how fine blocking attacks with your shield and attacking/grabbing out of it can be. Just make sure your enemy's hitbox is done.
If they grab after their attack, then you didn't punish them fast enough. You'll learn the optimal timings for un-shielding from enemy attacks, especially the multi-hit ones which are the trickier ones to un-shield from.
Rolling feels good, but it often doesn't accomplish too much when you are at the beginner stage of learning Competitive Smash. Don't get me wrong - use it for mobility and such, but stay focused when you're boxing in close range. Shield, figure out when their hitbox ends, and land a grab or jab combo.
Once you're better, you'll figure out the approaches that are nifty, safe, and lead to follow ups. Otherwise, a simple shield-jab combo will do the same damage as a non-combo fair or bair approach. Stick to the bread and butter, and move up to the fancy dishes when you're ready. Don't jump ahead yet, because you'll overwhelm yourself or get frustrated.
Keep it simple at first, basically, is what my advice is for new players.
Moving around too much and trying to look like the pros will overwhelm you and make you fumble, and also make you take your eyes off of your foe (oh yeah - look at the enemy fighter instead of your own).
Just focus on punishing and utilizing your current limited set of skills, and the rest will come in time. You'll move on to greater things, but not before you master the simpler basics.