Which method of gene amplification for toehold switches?
Option 2 is your simplest and easiest. It should give you unlimited plasmid to work from. Note that ordering pre-made sequences of this size isn't particularly cheap and might take a few weeks to get to your destination.
It may be easier (quicker + cheaper) to find a plasmid with the luciferase CDS and terminator already built in. You could then amplify this with primers incorporating your promoter and riboswitch sequences and some restriction enzyme sites to generate a product that looks like this:
RE1-ara-riboswitch-luciferase-RE2
You can then clone this into a(nother) plasmid cut with RE1 and RE2.
Another option is that if you have a plasmid with a luciferase gene in it already and a multiple cloning site (MCS) you can order complementary primers (note single-stranded DNA, anything less than about 150 bases is fine) containing the araC and riboswitch sequences flanked by two restriction sites, you then anneal the two primers, digest off the ends and ligate. You just have to be careful with making sure that everything is in-frame. I don't know anything about riboswitches though so frame may not matter so much.
As you have limited time I suggest buying chemically competent cells for heat-shock transformation (if you don't have some already); make sure you don't get electro-competent ones, as these will only work with an electroporator.  Also get a commercial mini-prep kit (e.g. Qiagen plasmid mini-prep). These are easy to use and reliable.
I think in option 1 you have something a bit odd going on - why would you digest your plasmid then re-ligate it, when it is already in the form that you are going to use?
I am not quite sure why in options 3 and 4 that you think that these are any different in terms of the end result to option 2.