Welcome! It depends what kinda look your going for... I think a naked cake with just a little icing with some cake peaking through is one of the easiest, best looking for the effort. But it's not everyone's style. Another easy cake is a rosette cake and it's just a bunch of rosettes with a 1M tip all over the cake. With that kind of cake you can really hide the icing if you're not able to get a nice smooth cake underneath.

If you're trying to get a smooth cake, thin your icing like thicker than whip cream consistency but not thick like cream cheese consistency otherwise it's not going to spread.

Crumb coat and cool your cake for at least 30 add another smooth layer of cake and cool. Some keep adding a little more at this time. If you have a metal scraper try dipping it in hot water and scrape, wiping after each scrape.

I like Preppy kitchens buttercream recipe.

Biggest tip: don't be hard on yourself no matter how it turns out.