Raising your own plants from seed generally works out a much less expensive than buying them. However obviously there is a Iot more work involved. Seeds have to be planted in trays or pots and kept moist and at a reasonably warm and constant temperature until germination. The seedlings then have to be pricked out and transplanted into larger pots or boxes before being moved to their final location in planters, containers or beds.
Some plants are easy to propagate and grow to maturity, others are very fussy from the the time they are "born" as regards temperature (and sudden changes of temperature), moisture, sunshine and nutrient requirements, ph of soil, resistance to mold and fungi, sensitivity to wind and heavy showers etc.
I've never grown morning glories and there are lots of species. French marigolds and pot marigolds (calendula) are annuals which are very easy to propagate. The large variety of aster species are also very showy and easy to grow also. Another option is to grow perennials. These become dormant and lose top growth in winter, but re-sprout in spring ( in a Mediterranean type climate I think they grow all year round). You can often propagate these by breaking bits off the the perimeter of the plant and potting up in compost.
The most important thing when sowing seeds (and when growing plants to maturity) is to keep the seed compost moist, but not saturated. More plants are drowned by generous gardeners than die from thirst! Temperature should be at least 17C (63F). Higher temperatures result in faster germination. Large seed should be pushed just below the surface, smaller seeds can be covered with a sprinkling of about 1/8 inch of fine compost. Very small seed shouldn't be covered at all. Check the packet to see what temp and sowing depth they recommend.
Its pretty much essential to sow your seed in sterile seed compost. If you use soil, bugs and molds will destroy the seeds before they get a chance to germinate. Once they become seedlings, you can transplant them into your homemade compost.