Hello from California. My favorite beginner patterns are straight-line blocks. Triple rail fence, 4-patch, 9-patch, log cabin.....none of them have curves, or bias edges (triangles). Some of them work really well with 2 or 3 different fabrics and the results are tried and true. The fact that you are asking questions as you are starting tells me that you are on the right track.
How do you become "passable?" Practice, cut with precision, sew an accurate 1/4" seam, press carefully, align blocks and pin when sewing blocks together, check along the way that everything lines up and before you know it - you'll be an old hand at this quilty thing. Most of all - have fun and don't beat yourself up when things don't turn out perfect.