The first trimester does the most structural work of a pregnancy and is often the hardest to feel good in.
Nausea, exhaustion, tender breasts and food aversions are common and usually settle by the second trimester. Their absence is not a warning sign — symptoms vary enormously between pregnancies in the same woman.
Some spotting is common in early pregnancy and does not necessarily indicate a problem. Bleeding heavier than a period, severe one-sided pain, or pain with shoulder-tip discomfort should prompt urgent medical contact.
Folic acid before and during early pregnancy has strong evidence behind it. Most other supplements have far less.