I weaned my first at 4 months - which was consistent with the advice at the time (she's 24). I was pleased to do it then because I had to go back to work when she was 5 months old and I was keen to get her new eating habits established before I went back. I don't know whether I'd do it as early now that the advice has changed, but that's up to you.
I didn't use rice or porridge. I made fruit or vegetable purées. The fruit ones were usually based on mashed banana, and I'd add a second fruit - for example pear, stewed apple, mango or kiwi.
The vegetable ones were either orange or green! The orange ones were various combinations of carrot, sweet potato and swede. Sometimes butternut squash I think too. The green ones were any combination of broccoli, spinach, courgette, and peas, sometimes along with potato mashed with expressed breast milk.
I introduced small quantities of meat, cheese and fish at 6 months.
My younger one had the same, but not until she was 5 months. I tried her earlier and she wasn't interested.