hi welcome another teenage fish keeper here
do you no what kind of pleco you have? as it will most proply grow out of the new tank
as for test kits personally i never bother with them ive done one test and never even new if it was good or bad so didnt try again
for fish a few ease to keep tropical fish would be livebearers eg. guppies, platys and sword tails. gourmis are another nice addtion to the bigginers tank and also a bigger school of tetras like somebody already said but as shae said at the end of the day its up to you on what you like and what you think looks good
oh and where abouts in nz are you
cheers