"In serious need of some tips"
Play Marth then
Ok, Bowser advice. Don't worry about having not many true combos. Bowser benefits much more as a punishing character, and his high speed lets him do this much more effectively. Bowser benefits from dashing in and shielding. Though it is not quite as effective as before the shield stun changes, it's still useful. He has great grab range and his Up B out of shield is stellar so these work well. Approaches should be varied from you actually approaching occasionally, to forcing the opponent to approach. Short Hop Air Dodge is good if you time it just right, as you can land with an Up B and approach that way. It's a good way to get past projectiles. Short Hop Forward Air is a good option at close range. You can do this retreating to be safe and also force the opponent to come to you. It autocancels too so it is relatively safe. Most times too, you can do this as an approach option as if the opponent shields, you can cross up their shield. Fire Breath is good too. Try jumping into it. It is also good to B reverse and Wavebounce it too. Run away from your opponent and if they follow you, B reverse it. Wavebounce into it and trick the opponent. Remember to angle it upwards slightly so people are caught into it for longer. Empty short hop into Side B is also good because opponents will often shield when you jump towards them. Jab is fantastic at close range too. Use it as a get off me move. Jab 1 into Ftilt or Dtilt too. Pivot Ftilt is also a good option when maneuvering around your opponent. Also, remember that Up Smash is fantastic for challenging opponents coming downwards, as the shell is fully invincible during the move.
Don't rush to get down to the stage. If anything, go back to the ledge. You are invincible when you grab the ledge the first time for a while so if you are close to the edge of the stage, go there. If you practice, try and Down B the ledge. This is safer as you basically throw a hitbox out stopping opponents challenging you, and you can grab the ledge during the animation.
Actually, Fthrow is a great kill throw at around 130% IIRC. Bthrow is also good, killing about 10% later I think.
Don't give up, and don't feel disheartened. Remember, Bowser is heavy and big. He gets combo'd easily. However, he lives to insane percentages, so think of it this way. If the opponent combos you, your attacks get better at punishing thanks to the rage. Don't get overly aggressive if you get a stock behind. I used to do this all the time with whoever I used. With a character like Bowser however, it is far worse, as he has lots of cooldown on his moves.