I think that a cake from scratch will always taste much better than a mix from a box; and if you use the freshest and best ingredients you can afford, you'll get a good result for sure.
There's a lot of knowledge and experience on this forum, and some members here have helped me a great deal in the short time I've been here. So, don't be afraid to ask.
Here's a nice little cake recipe that I learned how to master many years ago, before moving onto other things. It's a Victoria Sandwich, and it's very easy.
200g self raising flour
200g unsalted butter
200g golden caster sugar
1 teaspoon of baking powder
4 eggs
1 tablespoon of milk
1 teaspoon of vanilla extract
Pinch of salt
Butter and base line two 8 inch non-stick sandwich tins using parchment paper. Pre-heat your oven to 150 (fan) or 170C.
Put all of your ingredients into a large bowl and beat with a hand mixer until just combined. Scrape down the sides of your bowl with a spatula and quickly beat again for about 10 seconds. The trick with this cake is to beat as little as possible but just enough to combine everything perfectly - that way you'll end up with a lovely light cake.
Spoon the batter evenly between each of the tins and smooth over gently. Bake for 30 minutes, but check after 25 minutes. The cakes are done when you lightly press the middle and it springs back - if it leaves a mark, then put it back in the oven for a few more minutes. The cakes will also be coming away from the sides of the tin when they are done.
Leave to cool in their tins for 10 minutes before carefully turning out. Loose bottomed tins are a godsend for this type of cake!. Cool completely before spreading with strawberry or raspberry jam, and sandwiching together. A liberal sprinkling of icing sugar tops it off a treat!
Here's one I made earlier