Tetras need to be kept in groups of more than 4 and 5. 6 should always be considered an absolute minimum.
Wouldn't put guppies in with that lot. The tetras will fin nip, and the Rams will defend a territory and chase everything from it. Plus they need to be kept in a ratio of 1 male to 2-3 females, or same-sex shoals of more than 6.
The Rams need absolutely superb water quality. NO ammonia or nitrite, nitrate of less than 20ppm (less than 15 to be on the safe side) and pH should be steady at 6-6.5 (pH is much more important than many on here realise). Not a beginner fish, so wait for at LEAST a year before you think about getting them. One might suffer from subordinate stress if they don't pair-bond.
Apart from that, yeah, that should be do-able in a 30gal.
Plants:
Java Fern
Amazon Swords
Riccia
Hornwort
Wisteria
Anubias sp
Vallis
All of them should be pretty tough.
Make sure you cycle the tank before you get any fish though. To cycle a tank, you add a source of ammonia every day and test the water until ammonia and nitrite reach 0ppm and stay there for a week. For that, you need a test kit.
More details of the fishless cycle below: